CERC RAID5 performance lower than everyone else

[Jim Nelson]

John Hodrien wrote:
> On Fri, 18 Jul 2008, Adam Nielsen wrote:
> 
>> Hi all,
>>
>> When researching the poor performance on the CERC SATA controller in a
>> PE1800 here, I noticed that many people complain that they can't get
>> speeds faster than ~40MB/sec read/write.
>>
>> What I'd like to know is how on earth people are getting speeds that
>> high!  We've got five 160GB disks in RAID5, and I've yet to see read or
>> write speed go above 7MB/sec.
>>
>> This is painfully slow, and while we've managed to crawl along for a
>> while now it's really beginning to show.  Unfortunately it's still at
>> least a year away before we can justify replacing the machine, so if
>> anyone is able to offer any pointers as to how we can speed up the CERC
>> in the meantime they'd be much appreciated!
> 
> Sounds reasonable to me.  I gave up on RAID 5 and switched to RAID 1.  When
> the performance of that sucked I then dropped to software RAID 1.  That's got
> it up to a stunning 25Mbyte/sec write speed.
> 
> The card is awful.
> 
> jh
> 

Actually, it performs better than some of the 1st-gen 6-port LSI SATA RAID cards 
we purchased at about the same time.  Those got about 4 MB/sec... And that was 
with 2.4 or 2.6 kernels, and the fastest I got was with about 4.5 MB/sec with a 
custom kernel optimized for hard disk access.

We had 1.2 TB attached to that LSI card.  It took a long, long time to move our 
data over from that SC1600 when we finally retired it.  Good thing it was just 
archival storage.