Providing information lifecycle management (ILM) functions from within a single disk array is a hard thing to do. 3PAR's InServ array presents virtualised, multi-service tier disk storage with Utility Data Life Cycle Management (uDLM) features. Pillar Data also does this. Compellent does not. It presents virtualised multi-tier disk storage from a grid-like set of arrays.
Compellent is an InfoWorld award winner based on the 'extensive management, strong performance, great scalability, and superb ease-of-use' of its Storage Centre product. Like 3PAR it provides thin provisioning in which applications are only given the disk space they need to store data instead of a whole volume. The array maintains a buffer space of spare disk space and alerts Sysadmins to buy more when it starts running out. Customers need buy less disk up front. How does it do ILM?
Compellent virtualises storage at the block level. Its technology can support different categories of disk hardware; Fibre Channel or SATA say, and its software automatically track usage, and migrate data between storage classes based on user-defined rules.
3PAR also virtualises storage at a low level in its InServ array. It supports different hardware disk categories and different service levels to provide its Utility DLM functions.
Pillar Data virtualises its Axiom storage and presents different service classes based on a unique technology. This is that data stored on the outer edges of a drive is faster to access than data stored closer to the middle of the disk, because the head has less distance to move. Consequently different classes of array service are offered based on the position of the tracks on the disk surface. Data is striped across multiple drives to provide the capacity needed. Pillar provides four service levels, using Serial ATA (SATA) drives, and claims to offer Fibre Chanel-class disk performance with its fastest tier.
Data is migrated between tiers in its ILM function.
3PAR is probably the market leader of these three with the most customers and largest revenue numbers. Pillar Data only launched last year. Compellent likewise is a relatively new company. All three have garnered rave reviews from customers, and the storage media, for their technology.
Craig Nunes, 3PAR VP Marketing, says: "I pull for all the small guys. I love to have folks like Pillar out there. I think they've taken a quality of service level with only a dozen parameters and associated it with different hardware resources - and put it on an ATA-based array using inner-to-outer tracks."
"It's not well-suited to front rank data (but) okay for something that doesn't need a lot of on-line access." He doesn't think there will be significant differences bewtween the various service levels based on the different track location areas on the disks.
John Taffinder, 3PAR's EMEA VP, agrees: "Going from the outer to the middle tracks - what is the performance improvement? It's measurable but probably not significant."
Overall Nunes thinks: "Their idea that quality of service is based on where data is located on the disks is a little bit simple."
Interestingly Oracle is one of 3PAR's backers. Oracle boss Larry Ellison is the one and only backer of Pillar Data through his Tako Ventures business.
According to a Pillar Data spokesperson: "Pillars (ILM) quality of service (QoS) is not just on the disk but throughout the total system (Slammer, Fabric, Brick, Disk). This is a key differentiator for the Pillar system against the competition in the market.
QoS is not simply a matter of data placement on a disk or even different classes of disk. (Disk banding or short stroking has been around for long time.) It is the holistic product of intelligent queuing algorithms, meaningful cache management as well as intelligent disk placement. Those who think that it is a product of the disk are missing a trick. With the Pillar Axiom QoS and intelligent data layout, its SATA drives will far outperform the EMC low cost FC drives and provide better utilisation.
Discussing Compellent, Nunes says: "It's a little different (with) interesting technology. (It's) targetting SMBs, a different space from ours. We think of scalability of 150TB or so. Compellent thinks of scalability in much smaller numbers."
"Compellent is akin to a grid of boxes. Our technology is more of a grid-in-a-box. You need multiple nodes, multiple controllers to deal with a data set. With Compellent you can't parallelise different controllers in a data set."
A Compellent spokesperson said: "3PAR has a great system marketed primarily at large enterprises (50 TB and larger typically) that require their level of multi-node (controller) clusters. They, like Compellent, offer thin provisioning. Still, even with their scaling, they dont offer the same level of scaling and flexibility as Compellent. Were not familiar with what they offer for ILM/Data Progression. Compellents ability to automatically move blocks of data to the optimal tier of storage is very unique."
It looks as if 3PAR's Adaptive Provisioning technology, now under development, will at least match this dynamic block movement with a dynamic chunk movement capability.
Flexibility and reduced cost of ownership
All three suppliers, 3PAR, Compellent and Pillar, claim to offer terrific flexibility and sharply reduced storage costs through lower hardware purchase levels and much easier management. They have customers that love their products and technology reviewers providing plaudits.
All three offer a start small and grow big capability. This means that if you have a new application needing storage you could have a look at their offerings and see how their virtualisation and ILM facilities compare in practice with those offered by the tier one storage system vendors, such as EMC, HDS, HP, IBM and Sun. It could be that you get a pleasant surprise.