Steinar H. Gunderson wrote:
> On Wed, Jan 18, 2006 at 01:58:09PM -0800, William Yu wrote:
>> The key is getting a card with the ability to upgrade the onboard ram.
>>
>> Our previous setup was a LSI MegaRAID 320-1 (128MB), 4xRAID10,
>> fsync=off. Replaced it with a ARC-1170 (1GB) w/ 24x7200RPM SATA2 drives
>> (split into 3 8-drive RAID6 arrays) and performance for us is through
>> the ceiling.
>
> Well, the fact that you went from four to 24 disks would perhaps be a bigger
> factor than the amount of RAM...
>
> /* Steinar */
Actually no. Our 2xOpteron 244 server is NOT fast enough to drive an
array this large. That's why we had to split it up into 3 different
arrays. I tried all different RAID configs and once past about 8 drives,
I got the same performance no matter what because the CPU was pegged at
100%. Right now, 2 of the arrays are just mirroring each other because
we can't seem utilize the performance right now. (Also protects against
cabling/power supply issues as we're using 3 seperate external enclosures.)
The 1GB RAM is much bigger because it almost completely hides the write
activity. Looking at iostat while all our jobs are running, there's
almost no disk activity. If I manually type "sync", I see 1 big
250MB-500MB write storm for 2 seconds but otherwise, writes just slowly
dribble out to disk.
