iSCSI Requirements draft-haagens-ips-iscsireqs-00.txt Randy Haagens Director, Networked Storage Architecture Hewlett-Packard Co. Randy_Haagens@ hp.com 05 J ul 2000 P age 1
Applicability (Scope) • iSCSI is a mapping of SCSI-3 to TCP, a “SCSI transport” • Volume/ Block storage on IP Networks (L AN, MAN and W AN) • Analogous to today’s SAN architectures – Typically using Ethernet instead of Fibre Channel • Using SCSI protocol – SCSI for volume/ block storage (NFS and CIFS for file storage) • Gateways to other SCSI interconnects – Fibre Channel, Parallel-bus, potentially others • Benefit from IP/ Ethernet infrastructure • Increasing performance and reduced cost • Seamless conversion from local to wide area using IP routers • Emerging availability of “IP datatone” services • Protocols and middleware for management, security and Q oS • Economics arising from a single type of network R andy Haagens August 10, 2000 P age 2
Applicability (Scope) • Applications • L ocal storage access, consolidation and pooling • Remote disk access (as for a storage utility) • L ocal and remote synch and asynch mirroring between controllers • L ocal and remote backup and restore • Evolution with SCSI to support emerging object storage model • Topologies • Point-to-point direct connection • Dedicated storage L AN, consisting of one or more L AN segments • Shared L AN, carrying a mix of traditional L AN plus storage traffic • L AN-to-W AN extension using IP routers or carrier “IP datatone” • Private networks and the public Internet R andy Haagens August 10, 2000 P age 3
iSCSI Solution Topology WAN Service Campus Extension Controller WAN IP � HBA and driver Datatone Tape SCSI-TCP TCP connections dvr nic Gigabit Ethernet Gigabit Ethernet � Native tape � Protocol controller Wide area GbE Switch attachment extension Host computer with EtherSAN � FC Port controller (gateway) � Native array Controller Controller � SCSI Port attachment controller (gateway) JBOD JBOD Controller Controller Native storage array JBOD Tape FC hba hba H H Switch FC SAN Other SCSI peripherals hba H FC SAN Host computer with FC Controller Controller Controller JBOD JBOD JBOD What’s new FC array FC array R andy Haagens August 10, 2000 P age 4
iSCSI Solution Topology Site Network Corporate WAN Router Storage Management (only) Storage WAN Router HP-NT Management “Appliance” Storage Data (only) The two WANs may be combined, at some risk Storage to security and QoS networks are isolated between cells Servers Serv Storage Network Stor Remote console PC(s) Centralized Mgmt Controller Filer Controller Con ... ... Tape JBOD JBOD JB R andy Haagens August 10, 2000 P age 5
4.12 The SCSI model for distributed communications Initiator I/ O System Target I/ O System Client Server SCSI Application Protocol [26] Application equest → L ogical Unit Server R Client ← Server R esponse [5] equest → SCSI Application SAM and Command Device Service R Device Server ← Device Service R esponse [6] L ayer Standards [26] SAM -2 equest → SPC-2, SBC-2, &c. Task Management R Task Manager ← Task M anagement R esponse [6] SCSI Application SCSI Application ← P Protocol ← P P rocedure definitions here [SAM -2 §5,6,7] P P Confirmation rotocol Service rotocol Service R rotocol Service R rotocol Service Service Interface Indication esponse → equest → SCSI Protocol L ayer SCSI Protocol Standard a.k.a. SCSI Transport [26] [SAM-2 § 1.2] SIP, FCP-2, SBP-2, SCSI SCSI SCSI Protocol [26] SST, SVP, SSA- Protocol Protocol Services Services S3P/ SSA-TL 2, iSCSI/ TCP/ IP Physical Interconnect Service Interface Physical Interconnect Standard [26] Physical Interconnect Physical Physical Interconnect Interconnect L ayer Services Services SPI, SPI-2, FC-PH-3, FC-FS/ PI, FC-AL , Physical Interconnect [26] IEEE1394, Service Delivery Port Service Delivery Port SSA-PH-2, Service Delivery 802.2/ 802.3 Subsystem SCSI Device SCSI Device Composite of SAM -2 Fig.s 2, 5, 6, 7, 9, 26, 28 R andy Haagens 27 J ul 2000 P age 6
SCSI Multiport Target Unit SM U Domain Domain Service Service Device Device Delivery Delivery Subsystem Subsystem Interconnect Interconnect Target Target Service Service Subsystem Subsystem Delivery Port Delivery Port Target Identifier Target Identifier (64b) (64b) a.k.a. SCSI Device Identifier or Device Identifier §4.7.2 L ogical Unit O ne or more L UN s Task L ogical Unit (L U) M anager (L U) §4.7.4; §6 §4.8 O ne or more task sets Starts from 0. N ot a L U N umber Device Device Task Set Task Set per L UN . O ne per W W N . May be Identification (L UN ) (64b) Server “initiator” remapped. page (83h) §7 See §4.10.1 and SPC-2 SPC-2 §8.4.3 Untagged Tagged §8.4.4 for a discussion of Untagged Tagged Task Task Device Identifiers Task Task “L UN W W N ” iSCSI Architecture R andy Haagens 05 J ul 2000 P age 7
SCSI-layer Issues • Naming of SCSI targets and L Us • 64b Target ID limitation imposed by SAM-2 • Names vs. addresses of SCSI L Us • 3rd party copy (reference to L U) • Compatibility with new Access Controls model [T10/ 99-245 rev 8] • Multi-port device model • W hat exactly is a SCSI Service Delivery Port in the iSCSI session model? • In-order delivery of Task requests (commands) • SCSI attributes that control ordering of task execution depend on in- order task delivery • iSCSI layer is complicated by need to deliver tasks in order – Command numbering • Gateway architecture • Gateways to parallel SCSI and SCSI-FCP are contemplated R andy Haagens August 10, 2000 P age 8
iSCSI Multiport Target Unit SM U Domains are Domain Domain isolated networks Service Service Device Delivery Device Delivery Subsystem Subsystem Service Service Multiple target Service Service Target Target Interconnect Interconnect Target Target Delivery Delivery “views” Delivery Delivery Subsystem Subsystem Port(s) Port(s) Port(s) Port(s) preferred permitted iSCSI IP TCP L UN iSCSI IP TCP Target ID L UN iSCSI IP TCP Target ID L UN iSCSI IP TCP Session(s) Addr(s) Connection(s) M aps Session(s) Addr(s) Connection(s) (128B) M ap Session(s) Addr(s) Connection(s) (128B) M aps Session(s) Addr(s) Connection(s) a.k.a. SCSI Device Access Access Identifier or Device Access Access ID ID Identifier §4.7.2 ID ID L ist of Access IDs is Extend to an ACL accommodate url L ogical Unit Task L ogical Unit (L U) L UN Map used generally is a M anager (L U) function of the Service Delivery §4.7.4; §6 §4.8 P ort, Target ID and the Access ID. O ne or more task sets Starts from 0. N ot a L U N umber Device Device P referred implementation makes Task Set Task Set per L UN . O ne per W W N . May be Identification the L UN map a function only of (L UN ) (64b) Server “initiator” remapped page (83h) the Target ID; not all targets may §7 be reachable from a given See §4.10.1 and SPC-2 SPC-2 §8.4.3 Service Delivery P ort; Access ID Untagged Tagged §8.4.4 for a discussion of Untagged Tagged authorizes access to a given Task Task Device Identifiers Task Task “L U W W N ” Target. iSCSI Architecture R andy Haagens 27 J ul 2000 P age 9
iSCSI-layer Issues • Naming • URL syntax proposed: scsi:/ / <domain-name>[/ modifier] • Include SCSI “target” in name? Views, mapping • URL syntax: length problem (SCSI Target ID 64b limit) • Connection allegiance • SCSI task command/ data/ status in same TCP connection • Session Concept • A group of TCP connections • Supports ordered command striping for bandwidth aggregation • Recovery from TCP connection failure – SCSI task retry – “Replay buffer” may be required • Possibly need an iSCSI layer CRC • Concern about TCP’s checksum robustness • More end-to-end even than TCP R andy Haagens August 10, 2000 P age 10
SAM-2 Service Delivery Port 3.1.89 service delivery port: service delivery port: service delivery port: service delivery port: A device-resident interface used by the application client, device server or task manager to enter and retrieve requests and responses from the service delivery subsystem. Synonymous with “port” Initiator I/ O System (3.1.61) Client 4.6 …the Service Delivery Port object represents the hardware and software that implements the protocols and interfaces between servers or clients in the SCSI Device and the Interconnect Subsystem. Application 3.1.81 SCSI M ulti-port unit: SCSI M ulti-port unit: SCSI M ulti-port unit: A device that has multiple service delivery ports (see 3.1.89) or responds to multiple SCSI M ulti-port unit: Client SCSI device identifiers (see 3.1.79)... SAM-2, SCSI-3 Commands SCSI Application ← P Protocol P Confirmation rotocol Service rotocol Service R Service Interface equest → iSCSI iSCSI iSCSI iSCSI iSCSI FC-4 SCSI-FCP SCSI TCP TCP TCP TCP Protocol Services FC-3 Common Services IP IP IP IP Physical FC-2 Framing Interconnect FC-1 Coding 802.2 LLC / Ethernet Framing LLC LLC LLC Services (FC-FS) 802.3 Media Access MAC MAC MAC FC-0 Physical Service Delivery Port Physical PHY PHY PHY Interface (FC-PI) SCSI Device W ith channel bonding / port aggregation R andy Haagens 05 J ul 2000 P age 11
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