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Re: SSD + RAID

From: Karl Denninger <karl(at)denninger(dot)net>
To: Laszlo Nagy <gandalf(at)shopzeus(dot)com>
Cc: pgsql-performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: SSD + RAID
Date: 2009-11-13 13:02:34
Message-ID: 4AFD58EA.3030004@denninger.net (view raw or flat)
Thread:
Lists: pgsql-performance
Laszlo Nagy wrote:
> Hello,
>
> I'm about to buy SSD drive(s) for a database. For decision making, I
> used this tech report:
>
> http://techreport.com/articles.x/16255/9
> http://techreport.com/articles.x/16255/10
>
> Here are my concerns:
>
>    * I need at least 32GB disk space. So DRAM based SSD is not a real
>      option. I would have to buy 8x4GB memory, costs a fortune. And
>      then it would still not have redundancy.
>    * I could buy two X25-E drives and have 32GB disk space, and some
>      redundancy. This would cost about $1600, not counting the RAID
>      controller. It is on the edge.
>    * I could also buy many cheaper MLC SSD drives. They cost about
>      $140. So even with 10 drives, I'm at $1400. I could put them in
>      RAID6, have much more disk space (256GB), high redundancy and
>      POSSIBLY good read/write speed. Of course then I need to buy a
>      good RAID controller.
>
> My question is about the last option. Are there any good RAID cards
> that are optimized (or can be optimized) for SSD drives? Do any of you
> have experience in using many cheaper SSD drives? Is it a bad idea?
>
> Thank you,
>
>   Laszlo
>
Note that some RAID controllers (3Ware in particular) refuse to
recognize the MLC drives, in particular, they act as if the OCZ Vertex
series do not exist when connected.

I don't know what they're looking for (perhaps some indication that
actual rotation is happening?) but this is a potential problem.... make
sure your adapter can talk to these things!

BTW I have done some benchmarking with Postgresql against these drives
and they are SMOKING fast.

-- Karl

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  • SSD + RAID at 2009-11-13 12:46:15 from Laszlo Nagy

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