Re: [squid-users] IOWAIT and second disk

Adrian Chadd wrote:
> On Tue, Sep 19, 2006, Micha? Margula wrote:
>> Hello!
>>
>> I have a aufs on /dev/sdc. Iowait takes about 40% of CPU. If I add
>> another disk, will it make that load lower? Is it good idea to use two
>> disks with aufs (diskd is unstable unfortunately)?
>
> Yes, AUFS is fine.
>
> Take a look at http://www.squid-cache.org/~adrian/coss/ - note the dramatic
> drop in IOWAIT when using COSS.
>
> It also depends on the hardware you're using. What kind of disks are they?
> Which OS? Which controller?

Linux 2.6.15.1, /dev/sdc with cache is Seagate ST336754LC (Cheetach) -
36 GB, 15k RPMs, and logging is done on /dev/md0 which is RAID1
consisting of two disks like the one above. But I don't think RAID1
causes any trouble, iostat shows majority of IO operations on /dev/sdc
where cache resides.

Hardware is 2 x Xeon 3.6, 2GB RAM, SCSI storage controller: LSI Logic
53c1030 PCI-X Fusion-MPT Dual Ultra320 SCSI on Intel E7520.

Now in topic of COSS, what is better solution (/dev/sdc is 36 GB and
/dev/sdd also will be 36 GB, same disk model):

1) /dev/sdc and /dev/sdc used in full with AUFS and 1GB file of COSS in
memory
2) /dev/sdc with AUFS and /dev/sdd with COSS (wouldn't be 36 GB too much?)
3) /dev/sdc splitted for COSS and AUFS (if yes, what ratio of
splitting), /dev/sdd with AUFS
4) /dev/sdc and /dev/sdd splitted for COSS and AUFS

I thought that (1) would be OK. What do you think? What is recommended
size of COSS file?

-- 
Michał Margula, alchemyx@uznam.net.pl, http://alchemyx.uznam.net.pl/
"W życiu piękne są tylko chwile" [Ryszard Riedel]