Implementing datacentre flash arrays

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Techworld: I'd be interested to learn about the performance they have obtained, compared with the pre-MFT performance, both flash pre-MFT and disk.

Doug Dumitru: A lot of the applications that MultiValue databases host tend to be random write limited. Thus the usefulness of MFT. In terms of performance improvement, we have people who came off of 10K SCSI systems moving to single drive Samsungs and reports 15x improvements in the run-time of single-threaded batch jobs.

Techworld: What price did they pay for the flash SSD?

Doug Dumitru: Our existing customers are running servers that we built, with the exception of 1 dealer in Switzerland who builds their own white boxes. We price the flash drives as a part of a disk subsystem to cover the cost of the drives and our software. It usually works out to marking up the drives an additional 50% to cover the MFT license. Thus a 4 drive Raid-5 set with 32G Mtron drives will cost around $6000 including the controller and SATA bays. This gives you about 85GB of mountable space. Performance wise, doing 4K random IO with 10 threads, you get about 43,000 read IOPS and 25,000 write IOPS. This puts this array in the "160 15K SAS Drives" class, but the amount of space is obviously a lot smaller.

Techworld: How much capacity is involved?

Doug Dumitru: We use normal Flash disks. Right now, that means 32G and 64G drives from the mainstream vendors. While very large disks from people like bitMicro would work, they are far to expensive to make sense for us. We are very much positioned as a "middle market" solution.

MFT itself requires some space as "overcommit". For database applications we recommend 10%, but this is tunable from 5 percent upward. Dedicating more space can help out very busy database patterns, but most of the time this is hard to measure.

We can also use stock hardware to build Raid arrays. Because of the nature of MFT, RAID-5 works very well and RAID-10 is unnecessary. The biggest array we have tested is eight 32G drives. The biggest array that we think is practical is 32 64G drives or 2TB. This limit mostly has to do with direct attach and SATA issues. Because of how the current series of Flash SSDs work, we don't think they will scale well when used with SAS port expanders.