Message-ID: <4D9D502A.2010600@2ndQuadrant.com>
Date: Thu, 07 Apr 2011 01:48:26 -0400
From: Greg Smith <greg@2ndQuadrant.com>
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To: Jesper Krogh <jesper@krogh.cc>
CC: "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: Intel SSDs that may not suck
References: <4D90EDB6.2080609@2ndQuadrant.com> <4D9D3D4D.300@krogh.cc>
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On 04/07/2011 12:27 AM, Jesper Krogh wrote:
> On 2011-03-28 22:21, Greg Smith wrote:
>> Some may still find these two cheap for enterprise use, given the use 
>> of MLC limits how much activity these drives can handle.  But it's 
>> great to have a new option for lower budget system that can tolerate 
>> some risk there.
>>
> Drifting of the topic slightly..  Has anyone opinions/experience with:
> http://www.ocztechnology.com/ocz-z-drive-r2-p88-pci-express-ssd.html
>
> They seem to be "like" the FusionIO drives just quite a lot cheaper,
> wonder what the state of those 512MB is in case of a power-loss.

What I do is assume that if the vendor doesn't say outright how the 
cache is preserved, that means it isn't, and the card is garbage for 
database use.  That rule is rarely wrong.  The available soon Z-Drive R3 
includes a Sandforce controller and supercap for preserving writes:  
http://hothardware.com/News/OCZ-Unveils-RevoDrive-X3-Vertex-3-and-Other-SSD-Goodness/

Since they're bragging about it there, the safe bet is that the older R2 
unit had no such facility.

I note that the Z-Drive R2 is basically some flash packed on top of an 
LSI 1068e controller, mapped as a RAID0 volume.  It's possible they left 
the battery-backup unit on that card exposed, so it may be possible to 
do better with it.  The way they just stack those card layers together, 
the thing is practically held together with duct tape though.  That's 
not a confidence inspiring design to me.  The R3 drives are much more 
cleanly integrated.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support  www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books