Re: Question about performance with RAID disk

From: Scott Hess <>
Date: Fri, 22 Oct 1999 08:32:10 -0700

Anh-Tuan Doan <> wrote:
> We are running Squid in an Alpha box with squid cache directory in
> advfs, RAID5 disk (historical reasons) . We are going to change the box
> Sun or Linux boxes. Is it a good idea to use RAID or we'll have better
> performance if we use multiple harddisks (no RAID) for caching?

In general, you should just use multiple filesystems. Squid will balance
the load across them just fine. This guarantees that any given cache item
is on one, and only one, disk, which should give the best performance.
[With RAID, some portion of cached items will be spread across disks.] If
a disk dies, either idle it out or replace it with a fresh one, and let
Squid fill it back up.

RAID1 or RAID5 might make sense if the cached data was expensive. An
expensive Internet link might cause the cost of lost cached material to
exceed the cost of using RAID in the first place. Also, since Squid can
commit more items to the cache than the configured cache size, each
individual disk will need some seldom-used headroom, and RAID could let you
salvage that to a certain extent. And if an hour of downtime a couple
times a year to replace a drive might be killer, then it's hard to get
around needing RAID5 so that the hardware can mask the failures.

Of course, in the vast majority of uses, none of that makes a difference

Received on Fri Oct 22 1999 - 09:42:29 MDT

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