[SATLUG] new box built but not qutie happy

Brad Knowles brad at shub-internet.org
Sat Feb 9 16:19:26 CST 2008


On 2/9/08, toddwbucy wrote:

>  can someone recomend a low cost (yet reliable) raid controller card. I
>  am currently using a software raid 5 with 4 SATA2 320gig drives.  The
>  read performance is ok but the write really sucks.  So I am looking for
>  something that will help improve this or at least give me more options
>  then raid 0, 1, or 5.

This goes back to stuff that has been discussed before on this list, 
several times IIRC.

Performance-wise, software RAID (even RAID-5) is likely to perform 
better than hardware RAID, and usually much better, at least under 
"normal" conditions.  The CPU speeds on the RAID cards just hasn't 
been able to keep anywhere remotely close to the speeds of the main 
CPUs.

Where software RAID falls down is usually when there is a failure and 
you have to do a lot of stuff in the background to calculate the 
necessary parity bits and fill in the missing information, etc....


In my experience, this rule holds true pretty much all the way up to 
but not including the very largest disk storage devices that can be 
purchased from the likes of EMC, Hitachi Data Systems, etc....


You need to take a hard look at what is really hurting your 
performance, and do some deep debugging on your system.  It may be 
that buying extra non-RAID drive controllers may be enough to get 
your performance out of the doghouse (and probably a lot cheaper than 
a good performance RAID card), or there may be other things going on.

-- 
Brad Knowles <brad at shub-internet.org>
LinkedIn Profile: <http://tinyurl.com/y8kpxu>


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