IBM SAN Volume Controller - AbsoluteAstronomy.com

In computer data storage, the IBM SAN Volume Controller (SVC) is a block storage virtualization

Storage Virtualization

Storage virtualization or storage virtualisation is a concept and term used within computer science. Specifically, storage systems may use virtualization concepts as a tool to enable better functionality and more advanced features within the storage system.Broadly speaking, a 'storage system' is...

appliance that belongs to the IBM System Storage

IBM System Storage

IBM System Storage is the brand name for IBM's computer storage products, covering both Disk and Tape products.-DS3000 Series:The DS3000 products are made for IBM by LSI* DS3200...

product family. SVC implements an indirection, or "virtualization", layer in a Fibre Channel

Fibre Channel

Fibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards...

storage area network

Storage area network

A storage area network is a dedicated network that provides access to consolidated, block level data storage. SANs are primarily used to make storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers so that the devices appear like locally attached devices...

(FC SAN).

Architecture

SVC is always deployed as a cluster of nodes. Each node is a 1U high rack

19-inch rack

A 19-inch rack is a standardized frame or enclosure for mounting multiple equipment modules. Each module has a front panel that is wide, including edges or ears that protrude on each side which allow the module to be fastened to the rack frame with screws.-Overview and history:Equipment designed...

-mounted appliance based on an IBM System x

IBM System x

The IBM System x computers form a sub-brand of International Business Machines System brand servers...

server (SVC machine type is 2145). Each node has at least four Fibre Channel ports and is protected by a dedicated uninterruptible power supply

Uninterruptible power supply

An uninterruptible power supply, also uninterruptible power source, UPS or battery/flywheel backup, is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails...

. A node runs a Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

kernel and a specialized Virtualization Storage Software environment, that provides proprietary clustering capability. Each node has a service controller which provides a 2-row display, and a 5 button keyboard used to configure, service and monitor status.

SVC is based on COMmodity PArts Storage System (Compass) architecture, developed at the IBM Almaden Research Center

Almaden Research Center

The IBM Almaden Research Center is in San Jose, California, and is one of IBM's nine worldwide research labs. Its scientists perform basic and applied research in computer science, services, storage systems, physical sciences, and materials science and technology. The center opened in 1986, and...

. The majority of the software has been developed at the IBM Hursley Labs in the UK.

The SVC is a gateway device, meaning it sits between the hosts and the storage arrays, presenting itself to hosts as the target and presenting itself to arrays as the initiator. All FC ports on the SVC are both targets and initators, and all FC ports on all nodes MUST be zoned to each other to allow communication between the nodes and the transfer and mirroring of data.
An SVC cluster consists of several pairs of nodes (up to 4 pairs). Each pair of nodes is called an I/O group and provides write data cache

Cache

In computer engineering, a cache is a component that transparently stores data so that future requests for that data can be served faster. The data that is stored within a cache might be values that have been computed earlier or duplicates of original values that are stored elsewhere...

mirroring across the pair. In case of I/O

Input/output

In computing, input/output, or I/O, refers to the communication between an information processing system , and the outside world, possibly a human, or another information processing system. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it...

path failure, non-disruptive failover

Failover

In computing, failover is automatic switching to a redundant or standby computer server, system, or network upon the failure or abnormal termination of the previously active application, server, system, or network...

is performed inside I/O group only, via multipath

Multipath I/O

In computer storage, multipath I/O is a fault-tolerance and performance enhancement technique whereby there is more than one physical path between the CPU in a computer system and its mass storage devices through the buses, controllers, switches, and bridge devices connecting them.A simple example...

driver such as IBM Subsystem Device Driver (SDD) software.

Terminology

Node - a single 1U machine.

SVC node models
Type-model	Cache [GB]	FC speed [Gb/s]	iSCSI Speed [Gb/s]	Based upon	Announced
2145-4F2	4	2	n/a	x335	2 June 2003
2145-8F2	8	2	1	x336	25 October 2005
2145-8F4	8	4	1	x336	23 May 2006
2145-8G4	8	4	1	x3550	22 May 2007
2145-8A4	8	4	1	x3250	28 October 2008
2145-CF8	24	8	1	x3550M2	20 October 2009
2145-CG8	24	8	1 (10 Gbps optional)	x3550M3	5 May 2011

I/O group - a pair of nodes which duplicate each other's write commands.
Cluster - a set of up to 4 I/O Groups, which are managed as a single entity.
- Cluster IP address - a single IP address of a cluster that provides administrative interfaces via (SSH
  Secure Shell
  Secure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...
  
  and HTTP).
- Service IP address - an IP address used to service an individual node. Each node can have a service IP configured.
- Configuration node - a single node that holds the cluster's configuration and has the assigned cluster IP address.
Master Console - a management GUI for SVC, based on WebSphere Application Server
WebSphere Application Server
IBM WebSphere Application Server , a software application server, is the flagship product within IBM's WebSphere brand. It was initially created by Donald Ferguson, who later became CTO of CA Technologies, and the first version launched in 1998....

; not installed on any SVC node, but on a separate machine
- As of SVC code 6.x and greater, a Master Console is no longer used. Web based administration is done directly on the configuration node.
Virtual Disk (VDisk
Vdisk
In storage virtualization, virtual disk, or vdisk, is a virtual logical disk or volume to which a host or application performs I/O operations. Generally provided by a storage virtualization device and applicable mainly to Fibre Channel storage area network infrastructures...

) - a unit of storage presented to the host.
Managed Disk (MDisk) - a unit of storage (a LUN) from a real, external disk array
Disk array
A disk array is a disk storage system which contains multiple disk drives. It is differentiated from a disk enclosure, in that an array has cache memory and advanced functionality, like RAID and virtualization.Components of a typical disk array include:...

, virtualized by the SVC. An MDisk is the base to create an image mode VDisk.
Managed Disk Group - (MDisk Group) a group of one or more Mdisks. The extents of the MDisks in an MDisk Group are the base to create a striped or sequential mode VDisk.
Extent - an atomic unit of storage; an MDisk is divided into extents; a VDisk is formed from set of extents.

Software versions

Major releases
Release Code Level version.release.mod.fix (V.R.M.F)	Code Build Level
1.1.0.0	0.13.03070300
1.1.1.0	0.32.0311060000
1.2.0.0	0.53.0404190000
1.2.1.0	1.21.0410150000
2.1.0.0	2.16.0502180000
3.1.0.0	3.17.0511040000
4.1.0.0	4.25.0606010000
4.1.1.0	5.13.0611030000
4.2.0.0	6.17.0705210000
4.2.1.0	7.7.0711051000
4.3.0.0	8.16.0806230000
4.3.1.0	9.14.0811070000
5.1.0.0	17.8.0910292000
5.1.0.4	18.1.1005100000
5.1.0.5	18.1.1006120000
5.1.0.6	18.2.1007260000
5.1.0.7	18.2.1009060000
5.1.0.8	18.3.1011240000
5.1.0.9	18.3.1101260000
5.1.0.10	18.3.1104050000
6.1.0.0
6.2.0.4	36.7.1111040000
6.3.0.0

Performance

Release 4.3.0 of the SVC held the Storage Performance Council (SPC) world record for SPC-1 performance benchmarks, returning nearly 275K (274,997.58) IOPS (I/Os per second) with. There was no faster storage subsystem benchmarked by the SPC. The SPC-2 benchmark also returns a world leading measurement over 7GB/s throughput.

With the release of version 5.1 there are new test results using a 4 node and 6 node cluster with DS8700 as backed storage device. With this configuration, the IBM SVC broke its own record of 274,997.58 SPC-1 IOPS with 315,043.59 for the 4 node cluster and 380,489.30 with the 6 node cluster. The full results and executive summaries can be reviewed at the SPC website referenced above.

Features

As of release 4.3, the base major features of SVC are:

Indirection or mapping from virtual LUN to physical LUN

Servers access SVC as if it were a storage controller. The SCSI LUNs they see represent virtual disks (VDisks) which are allocated in SVC from a pool of storage made up from one or more managed disks (MDisks). A managed disk is simply a storage LUN provided by one of the storage controllers that SVC is virtualizing.

Data migration

SVC can move VDdisks from MDisk group to MDisk group, whilst maintaining I/O access to the data.

Use of existing LUNs via a feature called Image Mode

"Image" mode VDisk is a one-to-one representation of an MDisk (Backend LUN) which contains existing data; such an MDisk can be seamlessly imported into or remove out of an SVC Cluster.

Host LUN Mapping

The set of presented virtual LUNs (VDisks) can be configured independently for each server.

Fast-write cache

Writes from hosts are acknowledged once they have been committed into the SVC mirrored cache, but prior to being destaged to the underlying storage controllers. Data is protected by being replicated to the other node in the I/O group. Cache size is dependant on the model of SVC used.

Space-efficient features

LUN capacity is only used when new data is written to a LUN. Also known as Thin Provisioning

Thin Provisioning

Thin provisioning is the act of using virtualization technology to give the appearance of more physical resource than is actually available. If you always have enough resource to simultaneously support all of the virtualized resources then you are not thin provisioned...

Can be combined with the FlashCopy features detailed below to provide Space-efficient FlashCopy

Virtual Disk Mirroring

Provides the ability to make two copies of a LUN, implicitly on different storage controllers

The payment for base license is per TB

Terabyte

The terabyte is a multiple of the unit byte for digital information. The prefix tera means 1012 in the International System of Units , and therefore 1 terabyte is , or 1 trillion bytes, or 1000 gigabytes. 1 terabyte in binary prefixes is 0.9095 tebibytes, or 931.32 gibibytes...

of MDisks or per number of physical disk drives in the underlying layer. There are some optional features, separately licensed per TB:
Metro Mirror - synchronous remote replication

This allows a remote disaster recovery

Disaster recovery

Disaster recovery is the process, policies and procedures related to preparing for recovery or continuation of technology infrastructure critical to an organization after a natural or human-induced disaster. Disaster recovery is a subset of business continuity...

site at a distance of up to about 300km

Global Mirror

Global Mirror is an IBM technology that provides data replication over extended distances between two sites for business continuity and disaster recovery. If adequate bandwidth exists, Global Mirror provides an recovery point objective of as low as 3-5 seconds between the two sites at extended...

- asynchronous remote replication

This allows a remote disaster recovery site at a distance of thousands of kilometres.

FlashCopy

FlashCopy is an IBM feature supported on various IBM storage devices that makes it possible to create, nearly instantaneously, Point in Time copies of entire logical volumes or data sets. The Hitachi Data Systems implementation providing similar function is branded as ShadowImage...

(FC)

This is used to create a disk snapshot for backup, or application testing of a single VDisk. It requires 100% storage per copy (except when using Space Efficient VDisks as targets, described above), and is based on copy-on-write

Copy-on-write

Copy-on-write is an optimization strategy used in computer programming. The fundamental idea is that if multiple callers ask for resources which are initially indistinguishable, they can all be given pointers to the same resource...

technology (similarly to BCV

Business Continuance Volume

In disk arrays, a business continuance volume, or BCV, is EMC Corporation's term for an independently addressable copy of data volume, that uses advanced mirroring technique for business continuity purposes....

clone). One source volume can have up to 256 simultaneous targets. Targets can be made incremental, and cascaded tree like dependency structures can be constructed. Copy-on-write is based on a bitmap with a configurable grain size, as opposed to a journal

Journal (computing)

In computer storage, a journal is a chronological record of data processing operations that may be used to construct or reinstate an historical or alternative version of a computer system or computer file....

Other products running SVC code

On 7 October 2010, IBM announced the IBM Storwize V7000

IBM Storwize V7000

In Computer data Storage, the IBM Storwize V7000 is a midrange storage controller from IBM. The Storwize V7000 is based on the IBM SAN Volume Controller .- Hardware :...

. This uses the SAN Volume Controller code base with internal storage to provide a mid-level storage subsystem.

External links

Links to SVC Redbooks, info, updates

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.