On Wednesday 05 June 2002 01:51, Winston Gutkowski wrote:
> Thanks Henryk. Most informative.
> I'm interested in your figure of 3/5 for seek time on RAID 1
> though. Is this based on IDE or SCSI, software or hardware RAID?
No, simply RAID 1.
When you do RAID 1, all drives in the mirror (usually two) will be
involved on each write, and one of the drives will be involved on
read, almost degrading the number of spindles to the half compared to
using each drive individually.
If you have a crappy I/O system then the situation will always be
bad.. RAID or not..
> When I was at Sun I had to configure quite a few servers and we
> were told that, even with software RAID, a RAID 1 disk would
> generally outperform a single disk on reads and run @ 60-70% of a
> single disk on writes.
True, but two disks used in parallell gives you close to 200%
performance on both reads and writes, and considering that a Squid
workload consists of mainly small writes..
Also note that the SUN figures is based on a typical I/O workload
where quite many I/O operations are large, while the Squid I/O
workload is far from typical, with lots of small I/O randomly spread
out everywhere..
> PS: Really like the ability to shrink or expand a cache just by
> adding cache_dirs. Very nice. Do you have to stop and start squid
> to activate?
You will need to restart Squid when you delete a cache_dir. Adding can
be done at any time.
Regards
Henrik
Received on Wed Jun 05 2002 - 01:04:17 MDT
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