Backup Copies in a Flash
The primary enhancements found with SAN Volume Controller 4.2.1 are focused on additions to the FlashCopy functionality, namely Incremental FlashCopy and Cascaded FlashCopy.
There was a time, not all that long ago, when FlashCopy* functionality was available almost exclusively to enterprise-level organizations with deep pockets and high-end data storage devices, such as the DS8000* and earlier Enterprise Storage System* (ESS) offerings. In the rapidly evolving world of IT and with data storage becoming less expensive, however, the FlashCopy technology - sometimes referred to as point-in-time copy - is increasingly finding its way into the small and mid-sized business (SMB) space and providing a bridge between high-end and lower-end data storage devices.
The latest release of the SAN Volume Controller (SVC), for example, makes further use of its established FlashCopy capabilities. SVC V4.2.1 offers enhancements to its existing advanced copy functions, including the addition of Incremental FlashCopy and Cascaded FlashCopy. It also allows for dynamically configurable replication services and an increased capability to address data storage environments of up to 8 petabytes (PB).
"SAN Volume Controller has been available since July 2003, so it's been on the market for about four years, making it one of the most established storage-virtualization systems available, and certainly one of the most established of the major vendors," says Chris Saul, SAN Volume Controller Marketing Manager, IBM* Systems and Technology Group. "The 4.2.1 release enhances SVC in a number of areas, but particularly in the area of its copy-services flexibility."
What is SVC?
Specifically tailored to work with open-systems storage, SVC is a storage-virtualization system designed to provide a level of separation between how servers see storage and the way storage physically exists.
In most typical customer environments, there are multiple data-storage systems on the IT floor, in some cases from different vendors or even different types of systems from the same vendor - DS4000* and DS8000 systems together with EMC CLARiiON or EMC Symmetrix, for example. This mix of systems can make managing and using storage complicated because different disk systems tend to have different functions associated with them.
While all of the storage devices can make copies of data, a DS4000 copy function is different from a DS8000 function, and an EMC TimeFinder function operates quite differently from an IBM function - FlashCopy function. Customers are faced with using and managing those different sorts of replication functions. Additionally, various types of storage devices are usually administered in different ways, since they may have different administrative tools. A common cause of outages in datacenters is inadvertent mistakes on the part of storage administrators because having multiple systems administered in different ways can lead to more mistakes.
"What virtualization does is hide all the differences between the types of physical storage devices so all the storage appears as a single type of storage with a single set of common functions available," says Saul. "In the case of SVC, there's a single FlashCopy function, which works the same way across all supported storage devices. All of the storage is administered in the same way using a single set of tools, which reduces the risk of making mistakes and helps improve administrator productivity."
According to a Forrester Consulting report commissioned by IBM and released in September 2006, SVC was shown to double storage administrator productivity, particularly important for SMB customers that require more streamlined IT resources and personnel. In that same report, which focused on SVC customers, storage utilization was increased in some cases by up to 30 percent, and future storage growth was reduced in some cases by as much as 20 percent.
Architecturally, SVC is built around pairs of I/O groups called nodes. These nodes, or engines - based on IBM System x* machines - operate together in highly available pairs. Nodes are deployed in pairs to work together so if one fails, the other may continue operating. Depending on how the SVC system is scaled for performance, anywhere from one to four I/O groups work together in a cluster.
SVC hides the physical characteristics of the storage devices and pulls all available storage space across devices treating them all as a single pool of storage, which is a valuable resource for administrators to help them satisfy their business needs.
"That becomes really significant when you consider the replication and copy functions mentioned previously," says Saul. "With traditional storage, those functions operate within a single box, but with SVC those functions now operate across all the virtualized storage capacity a company may have. If you think about it, when you make a copy of data for backup purposes, you probably want to store the backup copy the cheapest way available to you, but you're probably making a backup copy because the information you're backing up is fairly important. The original data you'd probably want to store on high-performance, enterprise-class storage. With traditional approaches, a backup copy would need to be stored within the same enterprise-class storage, which is probably much more expensive storage than is necessary for a backup copy."
What is FlashCopy?
FlashCopy is a function designed to create an instant "copy" of some data. When an administrator issues a FlashCopy command that essentially says "make a copy of this data," SVC via FlashCopy immediately provides the appearance of having created a copy of the data, when in reality it creates the physical copy in the background before moving that copy to an alternative data-storage device, which can take some time depending on the size of the backup copy. However, it creates the appearance of having completed the copy instantaneously, so customers can have a backup copy available as soon as the command is issued, even though copying to a different storage medium takes place behind the scenes.
"Because it operates very quickly in this way, FlashCopy allows customers to make a copy and immediately move on to other work without having to wait for the data to actually physically be copied from one place to another," says Saul. "In that regard, SVC FlashCopy is very similar to FlashCopy on the DS8000, for example, with the difference being SVC FlashCopy operates on most storage devices attached to the SVC, spanning many different disk systems."