The IBM San Volume Controller (SVC) is a block virtualization storage appliance. SVC implements an indirection or "virtualization" layer in a Fibre Channel Storage Area Network (SAN).

Architecture

SVC is deployed as a cluster of nodes. Each node is a 1U high rack mounted appliance based on an IBM XSeries 335 or 336 server. Each node has four fibre channel ports and is protected by a Uninterruptible power supply. The nodes are clustered together so that surviving nodes can take over if a node fails.

SVC uses an in-band architecture which means that data flowing between a host and a storage controller flows into an SVC node and then back out onto the SAN. SVC presents an interface to a server which looks like a storage controller and an interface to a storage controller that looks like a server.

Features

As of release 3.1, the major features of SVC are:

Virtual LUN to Physical LUN indirection or mapping.

Servers access SVC as if it were a storage controller. The SCSI LUNs they see represent virtual disks 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 virtualising.

Data migration.

SVC can move data from mdisk to mdisk, whilst maintaining IO access to the data.

Importing existing LUNs via a feature called Image Mode

LUNs can also be backed out of virtualized mode

Host LUN Mapping.

This allows the set of vdisk that each host sees and the SCSI lun number at which each vdisk is presented.

Synchronous remote copy Metro Mirror.

This allows a remote Disaster recovery site.

Write-back Cache.

Writes from hosts are completed once they have been committed into the SVC cache but prior to be destaged to the underlying storage controllers. Data is protected by being replicated to the other node in the IO group.

Point in time copy IBM calls this FlashCopy.

This is used to create an online backup, for application testing or backup to tape.

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