Adaptec bolts SSDs onto lightning RAIDs
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Adaptec is adding a NAND flash cache to its RAID controllers to speed up disk array read I/O.
The company's MaxIQ product uses an Intel X25-E single level cell flash module which, Adaptec says, offers 1.2GB/sec throughout and 20,000 I/Os per second (IOPS) with a 3Gbit/s SAS interface and a PCIe 1.1 connection. It can be used on Adaptec's RAID 5xxx and 2xxx controller cards and existing users can upgrade to flash-enabled cards.
Data coming to applications from the drives is stored in the card's cache. Next time that data is required it is served from the cache, saving time-consuming disk I/Os. The cards plus MaxIQ software can be used without changes to the server host, its operating system or applications. An Adaptec controller could have up to four of the 32GB Intel modules installed.
Adaptec says MaxIQ can provide five times as many IOPS as a set of twelve Seagate 15K SAS drives in a web server application. The improvement was eleven-fold in a random read test.
There are higher capacity SSD alternatives available, but Adaptec says MaxIQ offers a lower cost/GB and a lower cost per IOPS than these. For example, it cites a PCI-e MLC (Multi-Level Cell) competitor - Fusion-io possibly - offering 800,000 IOPS at $15/GB and $0.15 per I/O. MaxIQ does a seemingly paltry 20,000 IOPS but costs $0.31/GB and $0.14 per I/O.
If the MaxIQ IOPS number is sufficient to accelerate a server plus application then Adaptec's RAID controller cache looks neat and cost-effective. It will enable Adaptec's OEMs, system integrator and VAR partners to implement SSD-cached JBODs (arrays constituting Just a Bunch Of Disks) and offer an instant performance pickup for virtualised, multi-core servers.
The focussed app areas include SQL, MySQL, virtual environments and web servers. Adaptec says its controller strategy going forward revolves around data conditioning: doing things with data in the I/O path between a server host's memory and the disk drives which an Adaptec controller manages. The company talks of high-performance hybrid arrays, a mix of controller flash cache and SAS and SATA disk drives. This is the first MaxIQ module and others will follow.
Overall the MaxIQ idea is pretty compelling and other RAID controller manufacturers might follow suit. It's a good design win for Intel.
The flash modules will be available to Adaptec's channel by the end of September and will cost around $1295.00. ®
COMMENTS
@Ian Michael Gumby & Annihilator
Well thanks for that, but you hardly added anything to what I said and I was aware of those issues. Oracle for one can spot full table scans and avoid populating the cache with unwanted data, but that wasn't foolproof (and it's changed again in Oracle). No caching algorithm is perfect - they can only forecast the future from past behaviour.
I was also fully aware of hybrid hard drives and that they've not provided the expected benefit. However, that is surely just because of the state of technology. I'm no fan of requiring motherboard and operating system support for such things - they really ought to be transparent, much as the cache in the controller will be. Whilst the former might produce some improvements through optimising for the peculiarities of particular environments, it's usually a technological dead end as it gets locked into your particular server hardware. Much better to be able to swap out with a fast I/O device.
The particular issue here was over the special characteristics of limited write cycles on SSD. Now I've never much worried about it on "true" write activity, as most I/O on most systems is read (there are exceptions to that where state information is updated and where reads are readily serverd from cache in a DB). However, if this device really does turn a whole bunch of what would have been reads into writes to the SSD then it could wear out faster. I would always assume that the things would be fail safe, it's really the cost implications.
Accurate stats?
"The company's MaxIQ product uses an Intel X25-E single level cell flash module which, Adaptec says, offers 1.2GB/sec throughout and 20,000 I/Os per second (IOPS) with a 3Gbit/s SAS interface and a PCIe 1.1 connection... MaxIQ does a seemingly paltry 20,000 IOPS but costs $0.31/GB and $0.14 per I/O... The flash modules... will cost around $1295.00."
Something doesn't seem right. First, those advertised specs for the X25-E are far higher than anything I've seen. Intel says the X25-E has sequential read bandwidth of 250MB/sec; that's a far cry from 1.2GB/sec.
Then there's the price. Adaptec says the MaxIQ offers a cost/GB of $0.31. If that was accurate, then either the MaxIQ's true price is $9.92 (not $1295.00) or it has a capacity of 4,177GB (not 32GB). Considering the selling price of an X25-E SSD ranges from $400 to $900, I'll go out on a limb and say the advertised cost/GB is nowhere close to accurate.
@Steven Jones
"Oh yes - and if a disk controllet can do this sort of caching, then it can be done in a drive. Add a few gig of SSD flash and some clever cache algorithms into a standard drive and we might well have something of use to the average PC user"
http://en.wikipedia.org/wiki/Hybrid_drive - not many turned up though as the advantage wasn't huge, but the costs were.
Failing that, it's already in use to an extent in Vista/7:
http://en.wikipedia.org/wiki/ReadyBoost
Caching algorithms have improved over the years you know, and can actually recognise when large backups are in progress. CPU designers have honed caching algorithms for several decades now. The SSDs won't fail over night, they'll just gradually reduce in capacity. Data won't be lost, performance will just gradually drop. Building it into the drives will exhibit the same effect.
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