3Ware 7500-4 Slow

[Eric Anderson]

Francisco wrote:
> On Mon, 5 Sep 2005, Chuck Swiger wrote:
> 
>> Small writes are pretty much the worst-case scenario for RAID-5,
> 
> 
> Such as mail servers?
> How about for a DB server which is mostly read only?
> 
>> normal to see a very significant performance drop-- by up to an order 
>> of magnitude-- from the performance of a bare drive.
> 
> 
> 
> At which point Raid 5 starts to perform better?
> 6,8,10 drives?
> 
> 
> How about RAID 10 for a DB server?
> I have been trying to convince the "powers that be" that SCSI would be 
> much better.. but the price difference is just too astronomical for the 
> capacities we need (500GB to 2 TB)
> 
> Even 10K RPM IDE drives seem like would be a problem since they are 
> mostly small in size.

I have a 16 disk SATA (WD Raptor 74GB drives) build with a RAID0+1 
(maybe called a RAID10 by others) connected via fiber channel, and I get 
extremely fast data rates with it.  A RAID0+1 is much faster at writes 
than a RAID5, and I believe faster at reads too.  I've gotten 
180-190MB/s from this disk, which is probably the most I could ask for 
on a 2gbit connection.

For databases, this is a great solution (I have a MySQL db running on 
one - never disk bound, ever).

I bought the array here:
http://www.acnc.com

They are FreeBSD friendly (and even support it too!) and have tools for 
FreeBSD as well as all the other OS's too.  I've had great luck so far 
with them.  One recommendation - get 1GB cache on the boxes - you'll see 
huge performance improvements for very little cost.

Eric



-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
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