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Haynes 3 Internet-Draft Primary Data 4 Updates: 5661 (if approved) August 29, 2017 5 Intended status: Standards Track 6 Expires: March 2, 2018 8 Requirements for pNFS Layout Types 9 draft-ietf-nfsv4-layout-types-07.txt 11 Abstract 13 This document defines the requirements which individual pNFS layout 14 types need to meet in order to work within the parallel NFS (pNFS) 15 framework as defined in RFC5661. In so doing, it aims to clearly 16 distinguish between requirements for pNFS as a whole and those 17 specifically directed to the pNFS File Layout. The lack of a clear 18 separation between the two set of requirements has been troublesome 19 for those specifying and evaluating new Layout Types. In this 20 regard, this document effectively updates RFC5661. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on March 2, 2018. 39 Copyright Notice 41 Copyright (c) 2017 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 2.1. Use of the Terms "Data Server" and "Storage Device" . . . 5 59 2.2. Requirements Language . . . . . . . . . . . . . . . . . . 6 60 3. The Control Protocol . . . . . . . . . . . . . . . . . . . . 6 61 3.1. Control Protocol REQUIREMENTS . . . . . . . . . . . . . . 8 62 3.2. Previously Undocumented Protocol REQUIREMENTS . . . . . . 9 63 3.3. Editorial Requirements . . . . . . . . . . . . . . . . . 10 64 4. Specifications of Original Layout Types . . . . . . . . . . . 11 65 4.1. File Layout Type . . . . . . . . . . . . . . . . . . . . 11 66 4.2. Block Layout Type . . . . . . . . . . . . . . . . . . . . 12 67 4.3. Object Layout Type . . . . . . . . . . . . . . . . . . . 13 68 5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 69 6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 70 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 71 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 72 8.1. Normative References . . . . . . . . . . . . . . . . . . 15 73 8.2. Informative References . . . . . . . . . . . . . . . . . 15 74 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 16 75 Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 16 76 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16 78 1. Introduction 80 The concept of layout type has a central role in the definition and 81 implementation of Parallel Network File System (pNFS). Clients and 82 servers implementing different layout types behave differently in 83 many ways while conforming to the overall pNFS framework defined in 84 [RFC5661] and this document. Layout types may differ as to: 86 o The method used to do I/O operations directed to data storage 87 devices. 89 o The requirements for communication between the metadata server 90 (MDS) and the storage devices. 92 o The means used to ensure that I/O requests are only processed when 93 the client holds an appropriate layout. 95 o The format and interpretation of nominally opaque data fields in 96 pNFS-related NFSv4.x data structures. 98 Such matters are defined in a standards-track layout type 99 specification. Except for the files layout type, which was defined 100 in Section 13 of [RFC5661], existing layout types are defined in 101 their own standards-track documents and it is anticipated that new 102 layout types will be defined in similar documents. 104 The file layout type was defined in the Network File System (NFS) 105 version 4.1 protocol specification [RFC5661]. The block layout type 106 was defined in [RFC5663] while the object layout type was defined in 107 [RFC5664]. Subsequently, the SCSI layout type was defined in 108 [RFC8154]. 110 Some implementers have interpreted the text in Sections 12 ("Parallel 111 NFS (pNFS)") and 13 ("NFSv4.1 as a Storage Protocol in pNFS: the File 112 Layout Type") of [RFC5661] as both being applying only to the file 113 layout type. Because Section 13 was not covered in a separate 114 standards-track document such as those for both the block and object 115 layout types, there had been some confusion as to the 116 responsibilities of both the metadata server and the data servers 117 (DS) which were laid out in Section 12. 119 As a consequence, new internet drafts (see [FlexFiles] and [Lustre]) 120 may struggle to meet the requirements to be a pNFS layout type. This 121 document gathers the requirements from all of the original layout 122 type standard documents and then specifies the requirements placed on 123 all layout types independent of the particular type chosen. 125 2. Definitions 127 control communication requirements: are for a layout type the 128 details regarding information on layouts, stateids, file metadata, 129 and file data which must be communicated between the metadata 130 server and the storage devices. 132 control protocol: is the particular mechanism that an implementation 133 of a layout type would use to meet the control communication 134 requirement for that layout type. This need not be a protocol as 135 normally understood. In some cases the same protocol may be used 136 as a control protocol and data access protocol. 138 (file) data: is that part of the file system object which contains 139 the data to read or written. It is the contents of the object 140 rather than the attributes of the object. 142 data server (DS): is a pNFS server which provides the file's data 143 when the file system object is accessed over a file-based 144 protocol. Note that this usage differs from that in [RFC5661] 145 which applies the term in some cases even when other sorts of 146 protocols are being used. Depending on the layout, there might be 147 one or more data servers over which the data is striped. While 148 the metadata server is strictly accessed over the NFSv4.1 149 protocol, the data server could be accessed via any file access 150 protocol that meets the pNFS requirements. 152 See Section 2.1 for a comparison of this term and "data storage 153 device". 155 fencing: is the process by which the metadata server prevents the 156 storage devices from processing I/O from a specific client to a 157 specific file. 159 layout: is the information a client uses to access file data on a 160 storage device. This information will include specification of 161 the protocol (layout type) and the identity of the storage devices 162 to be used. 164 The bulk of the contents of the layout are defined in [RFC5661] 165 as nominally opaque, but individual layout types are responsible 166 for specifying the format of the layout data. 168 layout iomode: is a grant of either read or read/write I/O to the 169 client. 171 layout stateid: is a 128-bit quantity returned by a server that 172 uniquely defines the layout state provided by the server for a 173 specific layout that describes a layout type and file (see 174 Section 12.5.2 of [RFC5661]). Further, Section 12.5.3 describes 175 differences in handling between layout stateids and other stateid 176 types. 178 layout type: is a specification of both the storage protocol used to 179 access the data and the aggregation scheme used to lay out the 180 file data on the underlying storage devices. 182 loose coupling: is when the control protocol is a storage protocol. 184 (file) metadata: is that part of the file system object that 185 contains various descriptive data relevant to the file object, as 186 opposed to the file data itself. This could include the time of 187 last modification, access time, end-of-file (EOF) position, etc. 189 metadata server (MDS): is the pNFS server which provides metadata 190 information for a file system object. It also is responsible for 191 generating, recalling, and revoking layouts for file system 192 objects, for performing directory operations, and for performing I 193 /O operations to regular files when the clients direct these to 194 the metadata server itself. 196 recalling a layout: is a graceful recall, via a callback, of a 197 specific layout by the metadata server to the client. Graceful 198 here means that the client would have the opportunity to flush any 199 writes, etc., before returning the layout to the metadata server. 201 revoking a layout: is an invalidation of a specific layout by the 202 metadata server. Once revocation occurs, the metadata server will 203 not accept as valid any reference to the revoked layout and a 204 storage device will not accept any client access based on the 205 layout. 207 stateid: is a 128-bit quantity returned by a server that uniquely 208 defines the set of locking-related state provided by the server. 209 Stateids may designate state related to open files, to byte-range 210 locks, to delegations, or to layouts. 212 storage device: is the target to which clients may direct I/O 213 requests when they hold an appropriate layout. Note that each 214 data server is a storage device but that some storage device are 215 not data servers. See Section 2.1 for further discussion. 217 storage protocol: is the protocol used by clients to do I/O 218 operations to the storage device. Each layout type specifies the 219 set of storage protocols. 221 tight coupling: is when the control protocol is one designed 222 specifically for that purpose. It may be either a proprietary 223 protocol, adapted specifically to a a particular metadata server, 224 or one based on a standards-track document. 226 2.1. Use of the Terms "Data Server" and "Storage Device" 228 In [RFC5661], these two terms of "Data Server" and "Storage Device" 229 are used somewhat inconsistently: 231 o In chapter 12, where pNFS in general is discussed, the term 232 "storage device" is used. 234 o In chapter 13, where the file layout type is discussed, the term 235 "data server" is used. 237 o In other chapters, the term "data server" is used, even in 238 contexts where the storage access type is not NFSv4.1 or any other 239 file access protocol. 241 As this document deals with pNFS in general, it uses the more generic 242 term "storage device" in preference to "data server". The term "data 243 server" is used only in contexts in which a file server is used as a 244 storage device. Note that every data server is a storage device but 245 storage devices which use protocols which are not file access 246 protocols (such as NFS) are not data servers. 248 Since a given storage device may support multiple layout types, a 249 given device can potentially act as a data server for some set of 250 storage protocols while simultaneously acting as a storage device for 251 others. 253 2.2. Requirements Language 255 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 256 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 257 document are to be interpreted as described in [RFC2119]. 259 This document differs from most standards-track documents in that it 260 specifies requirements for those defining future layout types rather 261 than defining the requirements for implementations directly. This 262 document makes clear whether: 264 (1) any particular requirement applies to implementations. 266 (2) any particular requirement applies to those defining layout 267 types. 269 (3) the requirement is a general requirement which implementations 270 need to conform to, with the specific means left to layout type 271 definitions type to specify. 273 3. The Control Protocol 275 A layout type has to meet the requirements that apply to the 276 interaction between the metadata server and the storage device such 277 that they present to the client a consistent view of stored data and 278 lock state (Section 12.2.6 of [RFC5661]). Particular implementations 279 may satisfy these requirements in any manner they choose and the 280 mechanism chosen need not be described as a protocol. Specifications 281 defining layout types need to clearly show how implementations can 282 meet the requirements discussed below, especially with respect to 283 those that have security implications. In addition, such 284 specifications may find it necessary to impose requirements on 285 implementations of the layout type to ensure appropriate 286 interoperability. 288 In some cases, there may be no control protocol other than the 289 storage protocol. This is often described as using a "loose 290 coupling" model. In such cases, the assumption is that the metadata 291 server, storage devices, and client may be changed independently and 292 that the implementation requirements in the layout type specification 293 need to ensure this degree of interoperability. This model is used 294 in the block and object layout type specification. 296 In other cases, it is assumed that there will be a purpose-built 297 control protocol which may be different for different implementations 298 of the metadata server and data server. The assumption here is that 299 the metadata server and data servers are designed and implemented as 300 a unit and interoperability needs to be assured between clients and 301 metadata-data server pairs, developed independently. This is the 302 model used for the files layout. 304 Another possibility is for the definition of a control protocol to be 305 specified in a standards-track document. There are two subcases to 306 consider: 308 o A new layout type includes a definition of a particular control 309 protocol whose use is obligatory for metadata servers and storage 310 devices implementing the layout type. In this case the 311 interoperability model is similar to the first case above and the 312 defining document should assure interoperability among metadata 313 servers, storage devices, and clients developed independently. 315 o A control protocol is defined in a standards-track document which 316 meets the control protocol requirements for one of the existing 317 layout types. In this case, the new document's job is to assure 318 interoperability between metadata servers and storage devices 319 developed separately. The existing definition document for the 320 selected layout type retains the function of assuring 321 interoperability between clients and a given collection of 322 metadata servers and storage devices. In this context, 323 implementations that implement the new protocol are treated in the 324 same way as those that use an internal control protocol or a 325 functional equivalent. 327 An example of this last case is the SCSI layout type [RFC8154], which 328 extends the block layout type. The block layout type had a 329 requirement for fencing of clients, but did not present a way for the 330 control protocol (in this case the SCSI storage protocol) to fence 331 the client. The SCSI layout type remedies that in [RFC8154] and in 332 effect has a tightly coupled model. 334 3.1. Control Protocol REQUIREMENTS 336 The REQUIREMENTS of interactions between the metadata server and the 337 storage devices are: 339 (1) The metadata server MUST be able to service the client's I/O 340 requests if the client decides to make such requests to the 341 metadata server instead of to the storage device. The metadata 342 server must be able to retrieve the data from the constituent 343 storage devices and present it back to the client. A corollary 344 to this is that even though the metadata server has successfully 345 given the client a layout, the client MAY still send I/O 346 requests to the metadata server. 348 (2) The metadata server MUST be able to restrict access to a file on 349 the storage devices when it revokes a layout. The metadata 350 server typically would revoke a layout whenever a client fails 351 to respond to a recall or a client's lease is expired due to 352 non-renewal. It might also revoke the layout as a means of 353 enforcing a change in locking state or access permissions that 354 the storage device cannot directly enforce. 356 Effective revocation may require client co-operation in using a 357 particular stateid (files layout) or principal (e,g., flexible 358 files layout) when performing I/O. 360 (3) A pNFS implementation MUST NOT allow the violation of NFSv4.1's 361 access controls: ACLs and file open modes. Section 12.9 of 362 [RFC5661] specifically lays this burden on the combination of 363 clients, storage devices, and the metadata server. However the 364 specification of the individual layout type might create 365 requirements as to how this is to be done. This may include a 366 possible requirement for the metadata server to update the 367 storage device so that it can enforce security. 369 The file layout requires the storage device to enforce access 370 whereas the flex file layout requires both the storage device 371 and the client to enforce security. 373 (4) Interactions between locking and I/O operations MUST obey 374 existing semantic restrictions. In particular, if an I/O 375 operation would be invalid when directed at the metadata server, 376 it is not to be allowed when performed on the storage device. 378 (5) Any disagreement between the metadata server and the data server 379 as to the value of attributes such as modify time, the change 380 attribute, and the EOF position MUST be of limited duration with 381 clear means of resolution of any discrepancies being provided. 382 Note that 384 (a) Discrepancies need not be resolved unless any client has 385 accessed the file in question via the metadata server, 386 typically by performing a GETATTR. 388 (b) A particular storage device might be striped such it has no 389 information regarding the EOF position. 391 (c) Both clock skew and network delay can lead to the metadata 392 server and the storage device having different values of 393 the time attributes. As long as those differences can be 394 accounted for in what is presented to the client in a 395 GETATTR, then no violation results. 397 (d) A LAYOUTCOMMIT requires that changes in attributes 398 resulting from operations on the storage device need to be 399 reflected in the metadata server by the completion of the 400 operation. 402 These requirements may be satisfied in different ways by different 403 layout types. As an example, while the file layout type uses the 404 stateid to fence off the client, there is no requirement that other 405 layout types use this stateid approach. 407 Each new standards-track document for a layout types MUST address how 408 the client, metadata server, and storage devices are to interact to 409 meet these requirements. 411 3.2. Previously Undocumented Protocol REQUIREMENTS 413 While not explicitly stated as requirements in Section 12 of 414 [RFC5661], the existing layout types do have more requirements that 415 they need to enforce. 417 The client has these obligations when making I/O requests to the 418 storage devices: 420 (1) Clients MUST NOT perform I/O to the storage device if they do 421 not have layouts for the files in question. 423 (2) Clients MUST NOT perform I/O operations outside of the specified 424 ranges in the layout segment. 426 (3) Clients MUST NOT perform I/O operations which would be 427 inconsistent with the iomode specified in the layout segments it 428 holds. 430 Under the file layout type, the storage devices are able to reject 431 any request made not conforming to these requirements. This may not 432 be possible for other known layout types, which puts the burden of 433 enforcing such violations solely on the client. For these layout 434 types: 436 (1) The metadata server MIGHT use fencing operations to the storage 437 devices to enforce layout revocation against the client. 439 (2) The metadata server MUST allow the clients to perform data I/O 440 against it, even if it has already granted the client a layout. 441 A layout type might discourage such I/O, but it can not forbid 442 it. 444 (3) The metadata server MUST be able to do storage allocation, 445 whether that is to create, delete, extend, or truncate files. 447 The means to address these requirements will vary with the layout 448 type. A control protocol will be used to effect these, whether a 449 purpose-built one, one identical to the storage protocol, or a new 450 standards-track control protocol. 452 3.3. Editorial Requirements 454 This section discusses how the protocol requirements discussed above 455 need to be addressed in documents specifying a new layout type. 456 Depending on the interoperability model for the layout type in 457 question, this may involve the imposition of layout-type-specific 458 requirements that ensure appropriate interoperability of pNFS 459 components which are developed separately. 461 The specification of the layout type needs to make clear how the 462 client, metadata server, and storage device act together to meet the 463 protocol requirements discussed previously. If the document does not 464 impose implementation requirements sufficient to ensure that these 465 semantic requirements are met, it is not appropriate for the working 466 group to allow the document to move forward. 468 Some examples include: 470 o If the metadata server does not have a means to invalidate a 471 stateid issued to the storage device to keep a particular client 472 from accessing a specific file, then the layout type specification 473 has to document how the metadata server is going to fence the 474 client from access to the file on that storage device. 476 o If the metadata server implements mandatory byte-range locking 477 when accessed directly by the client, it must do so when data is 478 read or written using the designated storage protocol. 480 4. Specifications of Original Layout Types 482 This section updates Section 12 of [RFC5661], which enumerates the 483 requirements of pNFS layout type specifications. It is not normative 484 with regards to the file layout type presented in Section 13 of 485 [RFC5661], the block layout type [RFC5663], and the object layout 486 type [RFC5664]. These are discussed here only to illuminate the 487 updates made to Section 12 of [RFC5661]. 489 4.1. File Layout Type 491 Because the storage protocol is a subset of NFSv4.1, the semantics of 492 the file layout type comes closest to the semantics of NFSv4.1 in the 493 absence of pNFS. In particular, the stateid and principal used for I 494 /O MUST have the same effect and be subject to the same validation on 495 a data server as it would have if the I/O were being performed on the 496 metadata server itself. The same set of validations are applied 497 whether pNFS is in effect or not. 499 And while for most implementations the storage devices can do the 500 following validations: 502 (1) client holds a valid layout, 504 (2) client I/O matches the layout iomode, and, 506 (3) client does not go out of the byte ranges, 508 these are each presented as a "SHOULD" and not a "MUST". Actually, 509 the first point is presented in [RFC5661] as both: 511 "MUST": in Section 13.6 513 "As described in Section 12.5.1, a client MUST NOT send an I/O to 514 a data server for which it does not hold a valid layout; the data 515 server MUST reject such an I/O." 517 "SHOULD": in Section 13.8 519 "The iomode need not be checked by the data servers when clients 520 perform I/O. However, the data servers SHOULD still validate that 521 the client holds a valid layout and return an error if the client 522 does not." 524 It should be noted that it is just these layout specific checks that 525 are optional, not the normal file access semantics. The storage 526 devices MUST make all of the required access checks on each READ or 527 WRITE I/O as determined by the NFSv4.1 protocol. If the metadata 528 server would deny a READ or WRITE operation on a file due to its ACL, 529 mode attribute, open access mode, open deny mode, mandatory byte- 530 range lock state, or any other attributes and state, the storage 531 device MUST also deny the READ or WRITE operation. Also while the 532 NFSv4.1 protocol does not mandate export access checks based on the 533 client's IP address, if the metadata server implements such a policy, 534 then that counts as such state as outlined above. 536 The data filehandle provided by the PUTFH operation to the data 537 server provides sufficient context to enable the data server to 538 ensure that for the subsequent READ or WRITE operation in the 539 compound, that the client has a valid layout for the I/O being 540 performed. 542 Finally, the data server can check the stateid presented in the READ 543 or WRITE operation to see if that stateid has been rejected by the 544 metadata server in order to cause the I/O to be fenced. Whilst it 545 might just be the open owner or lock owner on that client being 546 fenced, the client should take the NFS4ERR_BAD_STATEID error code to 547 mean it has been fenced from the file and contact the metadata 548 server. 550 4.2. Block Layout Type 552 With the block layout type, the storage devices are generally not 553 able to enforce file-based security. Typically, storage area network 554 (SAN) disk arrays and SAN protocols provide coarse-grained access 555 control mechanisms (e.g., Logical Unit Number (LUN) mapping and/or 556 masking), with a target granularity of disks rather than individual 557 blocks and a source granularity of individual hosts rather than of 558 users or owners. Access to block storage is logically at a lower 559 layer of the I/O stack than NFSv4. Since NFSv4 security is not 560 directly applicable to protocols that access such storage directly, 561 Section 2.1 [RFC5663] specifies that: 563 "in environments where pNFS clients cannot be trusted to enforce 564 such policies, pNFS block layout types SHOULD NOT be used." 566 Due to these granularity issues, the security burden has been shifted 567 from the storage devices to the client. Those deploying 568 implementations of this layout type need to be sure that the client 569 implementation can be trusted This is not a new sort of requirement 570 in the context of SAN protocols. In such environments, the client is 571 expected to provide block-based protection. 573 This shift of the burden also extends to locks and layouts. The 574 storage devices are not able to enforce any of these and the burden 575 is pushed to the client to make the appropriate checks before sending 576 I/O to the storage devices. For example, the server may use a layout 577 iomode only allowing reading to enforce a mandatory read-only lock, 578 In such cases, the client has to support that use by not sending 579 WRITEs to the storage devices. The fundamental issue here is that 580 the storage device is treated by this layout type in the same fashion 581 as a local disk device. Once the client has access to the storage 582 device, it is able to perform both READ and WRITE I/O to the entire 583 storage device. The byte ranges in the layout, any locks, the layout 584 iomode, etc, can only be enforced by the client. Therefore, the 585 client is required to provide that enforcement. 587 In the context of fencing off of the client upon revocation of a 588 layout, these limitations come into play again, i.e., the granularity 589 of the fencing can only be at the host/logical-unit level. Thus, if 590 one of a client's layouts is revoked by the server, it will 591 effectively revoke all of the client's layouts for files located on 592 the storage units comprising the logical volume. This may extend to 593 the client's layouts for files in other file systems. Clients need 594 to be prepared for such revocations and reacquire layouts as needed. 596 4.3. Object Layout Type 598 With the object layout type, security checks occur during the 599 allocation of the layout. The client will typically ask for layouts 600 covering all of the file and may do so for either READ or READ/WRITE. 601 This enables it to do subsequent I/O operations without the need to 602 obtain layouts for specific byte ranges. At that time, the metadata 603 server should verify permissions against the layout iomode, the file 604 mode bits or ACLs, etc. As the client may be acting for multiple 605 local users, it MUST authenticate and authorize the user by issuing 606 respective OPEN and ACCESS calls to the metadata server, similar to 607 having NFSv4 data delegations. 609 Upon successful authorization, the client receives within the layout 610 a set of object capabilities allowing it I/O access to the specified 611 objects corresponding to the requested iomode. These capabilities 612 are used to enforce access control and locking semantics at the 613 storage devices. Whenever one of the following occur on the metadata 614 server: 616 o the permissions on the object change, 618 o a conflicting mandatory byte-range lock is granted, or 620 o a layout is revoked and reassigned to another client, 621 then the metadata server MUST change the capability version attribute 622 on all objects comprising the file to in order to invalidate any 623 outstanding capabilities before committing to one of these changes. 625 When the metadata server wishes to fence off a client to a particular 626 object, then it can use the above approach to invalidate the 627 capability attribute on the given object. The client can be informed 628 via the storage device that the capability has been rejected and is 629 allowed to fetch a refreshed set of capabilities, i.e., re-acquire 630 the layout. 632 5. Summary 634 In the three original layout types, the burden of enforcing the 635 security of NFSv4.1 can fall to either the storage devices (files), 636 the client (blocks), or the metadata server (objects). Such choices 637 are conditioned by the native capabilities of the storage devices - 638 if a control protocol can be implemented, then the burden can be 639 shifted primarily to the storage devices. 641 In the context of this document, we treat the control protocol as a 642 set of requirements. And as new layout types are published, the 643 defining documents MUST address: 645 (1) The fencing of clients after a layout is revoked. 647 (2) The security implications of the native capabilities of the 648 storage devices with respect to the requirements of the NFSv4.1 649 security model. 651 In addition, these defining documents need to make clear how other 652 semantic requirements of NFSv4.1 (e.g., locking) are met in the 653 context of the proposed layout type. 655 6. Security Considerations 657 This section does not deal directly with security considerations for 658 existing or new layout types. Instead, it provides a general 659 framework for understating security-related issues within the pNFS 660 framework. Specific security considerations will be addressed in the 661 Security Considerations sections of documents specifying layout 662 types. 664 The layout type specification must ensure that only data accesses 665 consistent with the NFSV4.1 security model are allowed. It may do 666 this directly, by providing that appropriate checks be performed at 667 the time each access is performed. It may do it indirectly by 668 allowing the client or the storage device to be responsible for 669 making the appropriate checks. In the latter case, I/O access writes 670 are reflected in layouts and the layout type must provide a way to 671 prevent inappropriate access due to permissions changes between the 672 time a layout is granted and the time the access is performed. 674 The metadata server MUST be able to fence off a client's access to 675 the data file on a storage device. When it revokes the layout, the 676 client's access MUST be terminated at the storage devices. The 677 client has a subsequent opportunity to re-acquire the layout and 678 perform the security check in the context of the newly current access 679 permissions. 681 7. IANA Considerations 683 This document has no actions for IANA. 685 8. References 687 8.1. Normative References 689 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 690 Requirement Levels", March 1997. 692 [RFC5661] Shepler, S., Eisler, M., and D. Noveck, "Network File 693 System (NFS) Version 4 Minor Version 1 Protocol", RFC 694 5661, January 2010. 696 [RFC5663] Black, D., Fridella, S., and J. Glasgow, "pNFS Block/ 697 Volume Layout", RFC 5663, January 2010. 699 [RFC5664] Halevy, B., Welch, B., and J. Zelenka, "Object-Based 700 Parallel NFS (pNFS) Operations", RFC 5664, January 2010. 702 [RFC8154] Hellwig, C., "Parallel NFS (pNFS) Small Computer System 703 Interface (SCSI) Layout", RFC 8154, DOI 10.17487/RFC8154, 704 May 2017, . 706 8.2. Informative References 708 [FlexFiles] 709 Halevy, B. and T. Haynes, "Parallel NFS (pNFS) Flexible 710 File Layout", draft-ietf-nfsv4-flex-files-11 (Work In 711 Progress), July 2017. 713 [Lustre] Faibish, S. and P. Tao, "Parallel NFS (pNFS) Lustre Layout 714 Operations", draft-faibish-nfsv4-pnfs-lustre-layout-07 715 (Work In Progress), April 2014. 717 Appendix A. Acknowledgments 719 Dave Noveck provided an early review that sharpened the clarity of 720 the definitions. He also provided a more comprehensive review of the 721 document. 723 Both Chuck Lever and Christoph Helwig provided insightful comments 724 during the WGLC. 726 Appendix B. RFC Editor Notes 728 [RFC Editor: please remove this section prior to publishing this 729 document as an RFC] 731 [RFC Editor: prior to publishing this document as an RFC, please 732 replace all occurrences of RFCTBD10 with RFCxxxx where xxxx is the 733 RFC number of this document] 735 Author's Address 737 Thomas Haynes 738 Primary Data, Inc. 739 4300 El Camino Real Ste 100 740 Los Altos, CA 94022 741 USA 743 Phone: +1 408 215 1519 744 Email: thomas.haynes@primarydata.com