Cache is King
When it comes to SQL Server, you can never have enough memory. Yesterday I circled back to the topic of SSD due to the upcoming release of SSD technology from the Intel and Micron partnership. As you may have guessed, all SSD implementations are not alike. And, no matter what, RAM is the fastest data access available today.
I had a great deal of feedback on this topic. In fact, today I’ll be sharing feedback regarding SSD for Databases.
Ryan:
Personally, I think SSD drives are ready for prime time and many DBAs tend to be too conservative. They are currently cheap enough to allow replacement on failure. At prices around 200$ for a 120GB drive, it is only a fraction of the costs DBAs are used to. Having SSDs in a good SAN with proper RAID level and a fast replacement strategy should be secure enough for most applications and can provide fourfold performance improvement in comparison to SAS 15k rpm drives.
Additionally, since all widely available SSD drives are MLC and not SLC (10,000 write cycles Vs 100,000), there is no such thing as “Enterprise” SSDs. Enterprise-level SSD are SLC but the prices are so high that the advantage diminishes dramatically. It starts making sense buying consumer level SSDs because they have better performance than the Intel and HP ones. Besides Intel’s new 5 year warranty, there is no evident reason why SSDs for Database provisioning should not be the faster ones from vendors such as OCZ and Corsair.
These are just some thoughts I’ve been sharing with co-workers and fellow DBAs. I understand the fright around SSD failures, but as said before, I think a good replacement strategy and RAID (even software – that’s a whole other subject) should.suit most DBAs needs.
Brad:
I have used both Flash and DRAM based SSD on enterprise SQL Server systems
How I have used them:
Flash based ‘drive’ – relatively static data as you noted. Upside – cheap, pretty fast on read.
Downside – Some spinning disk can beat flash on read and write. There is no independent source of how long flash really lasts. Don’t know how/where the marketers/vendors are fudging the speed/reliability vs. time statistics. Most of the figures are statistical forecasts, not observed behavior. To the professionally paranoid DBA this implies a controller in front of the flash device that can bring a spare on-line transparently to other hardware/software (Added bucks).
DRAM based ‘drive’ – used for transaction logs & cut my log wait times by 66%+.
Upside – DRAM failure stats/modes well known. Does not age like flash.
Downside – Expense (These started as US DOD products, with the monster profit margin). The vendors need to reset their expectations – it’s only a RAM chip folks!. Usually bundled as part of a highly reliable array.
On the other hand, how much does RAM on the board cost & how much will you gain?
Upside – Again RAM is well-known and does not age out like flash. Fastest thing except CPU buffers, limited by bus speed. No new management/worries added.
Downside – More expensive than flash.
It is the usual reliability vs. money vs. speed. You have to choose for yourself.
Tomorrow I’ll share a lot of cool things people are doing with SSD for other non-server applications,.
Cheers,
Ben
SSWUG TV
With Stephen Wynkoop and Sam Brace
Here’s an episode of SSWUG TV you won’t want to miss with an interview from Itzik Ben-Gan, SQL Server MVP and co-founder of SolidQ.
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