Give your SAN to your SQL team. Part #1

Exchange 2010 is able to use virtually any storage you give it, the only criteria being that it supports the IOPS requirement for the workload demanded. Due to the efficiencies in the current version of the storage engine, that means that databases can now be stored on SATA disks, SAS disks, RAID volumes on DAS Shelves, or the holy grail of storage – Tier 1, the SAN.

Exchange 2010 promises to dramatically cheapen the cost of mail storage to the point where it no longer requires SAN based storage to achieve its goals of storing mail in a secure and highly available manner.

You may think that SATA is great when it comes to storing videos of the kids on holiday, old emails, documents and your music collection, and we agree. SATA has been the last thing we would have thought of in the modern datacentre, OR that mail server you hide under the desks or in the closet in your small branch office.

So how has SATA become the new rising star of storage, after previously only influencing the desktop sector?

There are two kinds of SATA we need to consider here, desktop or consumer SATA and enterprise SATA. The difference comes in the construction and the firmware of the disks. Enterprise SATA disks have more rigidity, more extra bits in the chassis and firmware that take into account that each disk may be housed in a shelf with a number of other disks which vibrate, spin and potentially influence each other.

Consumer SATA disks on the other hand have a much lower cost construction and are not designed with any of the additional heat or vibration considerations in mind.

So that makes sense – enterprise SATA disks can live amicably in a datacentre – but they’re still SATA. They’re still slow – literally slow. They rotate as slow as 5400 RPM, as opposed to the 10 000 or 15 000 RPM you’d expect from a traditional enterprise disk. Random seek times are what you’d expect, randomly slow. So how on earth do they become good candidates for the most important commodity in your digital life – your companies email?

The Exchange 2010 version of ESE – the Extensible Storage Engine, which is the database that Exchange uses, has a bit of secret sauce, actually it’s a rewrite from the ground up, which makes it 90% faster than Exchange 2003. That’s right, 90%, no typo there. But wait there’s more – it’s also optimised for sequential read and writes, in fact the entire database is logically laid out to accommodate long reads and long writes, exactly the kind of thing SATA disks are good for.

So let’s talk about the trust issues you may have with SATA – it’s STILL SATA, it’s still just a single disk, and just to top things, Microsoft are asking you to throw your RAID controller away as well. Is that still a real world expectation?

In part 2 we’ll have to have a quick look at how Exchange 2010 does High Availability for the database.

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