Analysis

posted on 11 April 2008 14:03

It's obvious isn't it; Pillar is so last year. Let Pillar duke it out with EMC and Netapp and 3PAR, yesterday's giants and today's wannabees; the future is clustered and unified storage arrays built with sealed canisters of disk drives as their building blocks. Revolution is here and Atrato and Xiotech are leading the charge.

That's a nice story. It's not true but it's a nice pitch. The reality seems to be that Pillar has made a fundamental architectural move shared with Atrato and Xiotech; it has split its array controller functionality into two levels. An upper level deals with array-level storage matters. A lower level deals with RAID and associated matters at a set of disk drives level. Thus Pillar's Slammer boxes contain the array-level intelligence, the Axiom O/S, whilst its Bricks deal with RAID intelligence for sets of six disk drives.

Xiotech's Emprise architecture has as its basic array building block the ISE or Intelligent Storage Element which contains either ten 3.5-inch drives or twenty 2.5-inch ones, and controlling intelligence. A Brick is Pillar's ISE. Unlike the ISE it isn't sealed and it doesn't contain so much remedial software for its disk drives but conceptually Brick and ISE are pretty much identical.

Xiotech says its ISEs contain a homogenous set of drives but that ISEs could contain all Fibre Channel or all SAS or all SATA drives and even solid state drives(SSDs). The same is true for Pillar's Bricks. Each one contains a set of identical drives but you can mix Fibre Channel and SATA Bricks in one Axiom system. SAS and SSD may well be coming.

Xiotech says that an Emprise will have a very low incidence of service engineer visits because of its fail-in-place technology. But Xiotech doesn't provide a numerical rating for this; there's no '5 nines' score for example.

Pillar's 500MC configuration has two Axiom arrays with the Slammers in an active:active failover configuration and a rating of 99.999 percent availability; 5 nines. Like the Emprise 7000, it will scale to a petabyte of mission-critical storage.

Pillar people could be forgiven if they look at Xiotech's new box and wonder what all the fuss is about.

The Atrato Velocity1000 is a second sealed canister array which the company says has accelerated I/O. Pillar's Bob Maness, VP world-wide marketing, says that as you add Bricks to an Axiom, the array's performance increases: "We can add up to 128 RAID controllers in a single system and no-one else comes close."

The Axiom aims to balance the three things an application needs from a storage array: capacity; I/O bandwith; and availability, and to scale these things and to deliver storage facilities geared to particular applications' needs; something neither Atrato nor Xiotech can do.

The essential attribute of the Atrato Velocity and Xiotech Emprise products isn't the fact they use sealed canisters but that they use a 2-level hierarchy of array controllers enabling them to devolve some of the array intelligence closer to sets of disk drives and have more balanced scalability as a result.

Granted they have more disk drive remedial intelligence but that is necessary because they use sealed canisters unlike Pillar's more accessible Bricks. In fact Pillar implemented an array building block based on sets of disk drives well before Atrato and Xiotech.

(IBM's XIV Nextra product also uses sets of disk drives as its array building block. They are called data modules. Front-end processing is performed by interface modules separate from the data modules; another 2-level controller hierarchy.)

Put that on one side though and what do end users actually get from the three company's arrays that is significantly different? Let's wait for comparable SPC scores to judge performance. Insofar as availability is concerned Pillar puts out a 5 nines number and Xiotech does not.

What you get from Pillar is a track record. What you get from Atrato and Xiotech remains to be seen. It could be great; it might even be wonderful. We'll just have to wait and see.

^{[Chris Mellor.]}