Wednesday, May 26, 2010

Excuse me Sir, this Violin seems out of Tune

By Mike Ault

In a recent article on the Channel Register website, Violin through Chris Mellor talks about their 3200 Flash Memory Array. Unfortunately in the release there are some claims that require examination if not repudiation. Let’s look at the claims put forth from Violin:
  1. Integrated Flash RAID and a sustainable 10-fold performance advantage over leading competitors
  2. Scales from 500GB to 10TB
  3. Data latency less than 100 microseconds
  4. Working life of 10+ years with continuous writes
  5. First memory array to scale to more than 140TB in a rack with performance over 2 million IOPS
  6. Total cost lowered by more than 50 percent
  7. Has RAID protection unlike Oracle’s Exadata
  8. Violin is the first company to aggregate Flash as an enterprise storage solution, beyond just a cache strategy
Let’s examine each of these claims.
  1. Integrated Flash RAID and a “sustainable 10-fold performance advantage over leading competitors”
    Wrong: While Violin may be an integrated Flash RAID, their only competitor in this market is Texas Memory Systems. Based on the proven 80 microsecond write times (per SPC Benchmark 1™) of the RamSan-620 products, obviously the 10 fold performance claim is patently false. Now in when compared to disks, this is true with virtually all Flash providers.
  2. Scales from 500GB to 10TB.
    Wrong: This doesn’t take into account the capacity that must be used for Flash management, wear leveling, RAID etc. Their actual usable capacity at the top end of the range is only 7.5 or so terabytes, compared to the actual usable capacity for the RamSan-630 of 10TB.
  3. Data latency less than 100 microseconds.
    Inaccurate: So, what is the reference point of this claim? Is this read, write, or a blended rate? If it is read, then what is write latency? The RamSan-500 provides 15 microsecond read latency (from cache), the RamSan-620/630 products provide 80 microsecond write latency and 250 microsecond read latency (nominal) with generally better latency than reported. In looking at the graphs of latency versus IOPS on the Violin site for the 3200, its latency rapidly increases above the reported 100 microseconds as IOPS increase.
  4. Working life of 10+ years with continuous writes.
    Inaccurate: Show me the numbers. Is this 365X24X7 at 220,000 IOPS with 100% writes? 80/20 read/write? As they used to say in math class…show your work. Just going by the numbers (I can send you a spreadsheet) the RamSan-630 with a full Flash load-out will last 27 years at 400K write IOPS, it will be on eBay before it wears out.
  5. First memory array to scale to more than 140TB in a rack with performance of over 2 million IOPS.
    Wrong: The RamSan-630 at 10TB usable capacity and 500,000 IOPS in a 3U form factor provides 140TB usable space and 7,000,000 IOPS in a single rack. It was announced in April 2010 (actually earlier than that, but that was the “official” date). The 3200 was announced in May 2010.
  6. Total cost lowered more than 50 percent.
    Inaccurate: More hand waving, break it down. For example, what are support costs, the cost of the needed head to provide RAID, and other costs? Total cost compared to what? For example the base cost of a 10TB RamSan-630 is $370K for a full capacity 10TB system ($36/GB usable), which is actually 13.5TB total giving $26/GB. At 200K for a Violin 7.5 TB system (usable) so while it is $20/GB for actual storage, for usable it is $26/GB. Essentially the price is a wash with no real benefit, it is just smoke and mirrors and nowhere near the claimed 50%.  At most a 38% difference, however, what else are they not giving all the facts about?
  7. Has RAID protection unlike Oracle’s Exadata
    Wrong: Exadata uses ASM technology which provides striping and mirroring (RAID10) in fact from the numbers reported for the Exadata of actual versus available capacity for an Exadata cell, Exadata appears to be using HIGH redundancy which means 3-way mirroring. So, wrong again, Exadata has RAID capacity and is RAIDed.
  8. Violin is the first company to aggregate Flash as an enterprise solution, beyond just a cache strategy.
    Wrong: TMS, with the RamSan-500 (2TB), RamSan-620 (5TB) and RamSan-630 (10TB) products provided the first aggregate Flash enterprise solution. The RamSan-500 was announced in September 2007, the RamSan-620 was announced in April 2009 and the RamSan-630 was announced in April 2010, the Violin 3200 in May 2010. Obviously it is fourth in line, not first.
With so many inaccuracies, can the actual specifications provided really be trusted?

Monday, May 3, 2010

Who's In Charge Here Anyways?

As DBAs we have all seen it, heck, probably done it. We call over to the server administrators for more space for our database files and sometime later we get it. We have no idea how it is configured, where it is located or if it will contend with existing file placements. All of the files we own are located in some magic land, let’s call it SAN Land, where everything is always load balanced, there are no hot spots and nothing ever contends with anything else. I think it is located right next to Lake Woebegone.

The SAN as a blackbox technology has been a boon and a bane to Oracle administrators. We know how things should be set up but when we try to pass along this information to the SAN administrator we hear the usual replies about how we have to co-exist with the other users and it is just not possible to configure things just for us. Well, those days have ended.

How about space that doesn’t have to be configured with an eye towards contention due to head movement or contention caused by block placement? How about freedom from hotspots and all the other problems which plague disk based technology? Even better, how about storage that can be locally managed? Impossible? Am I in a fantasy land somewhere?

Nope, not a fantasy land, welcome to the year 2010. How about 225 to 450 gigabytes of low latency storage that is locally controlled and doesn’t depend on disks, and better yet, can usually be purchased and installed with little pushback from system or LAN administrators? The RamSan-10 or RamSan-20 provide 225-450 gigabytes of high speed – low latency SLC flash memory based storage that plugs into a full size PCIe slot in the server and looks like another disk drive, but looks are deceiving.

As a “database accelerator” for a single server database that hooks directly into the server and doesn’t require any fibre channel, NFS, iSCSI or SAS connection, PCIe storage bypasses many of the management headaches associated with standard SAN technology. Due to the RamSans not being dependent on a physical device, 100% of the storage capacity can be utilized, no need to worry about short-stroking, striping or mirroring to get better performance. At a price of between 8-20K USD these solutions also fall easily within the signatory purchase powers of most department heads.

So shake off the fetters of the SAN world and step into the 21st century! Deliver 5 times the performance of standard SAN technologies to your database that you control locally.