[CentOS] 3ware 9550 series

[Troy Engel]

David Thompson wrote:
> Peter =?iso-8859-1?q?Kjellstr=F6m?= wrote:
>> raid5, #2 I can't get good read performance on two raid5s in a lvm stripe).
> 
> Yeah, we've also seen performance issues with raid5 on the 9500 series 
> products.  The benchmarks we run look good, but when we've put them into 

As per an old thread on the list, I have a new 9500S-12 and am seeing 
the same performance problems. But, I'm fairly sure it's because without 
the BBU installed write-cache is disabled. I have ordered the BBU and 
expect here soon, I'll see if I can't post some pre-BBU/write cache and 
post-BBU/write cache numbers, if I find a good test.

Right now I'm running Arkeia on it as the backup-to-disk, and in the 
middle of the heaviest use I'm seeing about 50-60% I/O wait, horrible. 
I'm hoping the write cache is going to help this a lot. (*)

-te

(*) some sar output:

12:00:14 AM   CPU   %user   %nice  %system  %iowait  %idle
12:10:51 AM   all    6.44    0.03     4.19    51.05  38.30
12:10:51 AM     0    3.83    0.02     4.28    49.69  42.18
12:10:51 AM     1    9.06    0.03     4.09    52.40  34.41
12:20:08 AM   all    7.45    0.02     4.40    52.52  35.61
12:20:08 AM     0    4.08    0.02     4.58    51.36  39.96


-- 
Troy Engel | Systems Engineer
Fluid, Inc | http://www.fluid.com