RE: [squid-users] disk partition locations ?

> -----Original Message-----
> From: john allspaw [mailto:jallspaw@yahoo.com]
> Sent: Monday, September 12, 2005 7:58 AM
> To: Henrik Nordstrom; Squid Users
> Subject: Re: [squid-users] disk partition locations ?
>
>
> thanks for the replies, guys.
>
> yes, we're using squid in a farm with very high performance
> requirement, as it's doing http acceleration for our origin servers.
> we're replacing 2disk SATA with 6disk SCSI, and while I
> gather there are diminishing returns with adding over 3 or 4
> spindles, having a decent cache size is probably second in
> importance. 
>
> we'll be going from 2 cache_dirs of 10Gb each to 6
> cache_dirs (one on each disk) with 5Gb each.
> our cache_mem size is 2048mb, which puts us just over the
> 10mb/1Gb mem-to-disk suggestions, but the boxes have 4Gb of

As I understand it, squid only populates cache_mem with newly requested objects (not objects from disk), so if you restart Squid, that 2GB of RAM is going to lay fallow. Using a smaller cache_mem allows the OS to use the rest of the memory to cache disk hits.

The 10mb/1GB mem-to-disk suggestion is how much ADDITIONAL memory squid uses (for overhead, and the like):

"As a rule of thumb on Squid uses approximately 10 MB of RAM per GB of the total of all cache_dirs (more on 64 bit servers such as Alpha), plus your cache_mem setting and about an additional 10-20MB. It is recommended to have at least twice this amount of physical RAM available on your Squid server."
 
> RAM in them, and we can add more if need be.  we're doing
> roughly 3000 req/sec across an 8 machine farm, and these SATA
> drives are getting awfully hot, with over an 80% hit rate
> (40% mem, 40% disk).  the objects never change once they are
> in cache except for small cases, in which case we make an
> explicit PURGE.
>
> we see upwards of 80-100% disk utilization at peak, so
> getting the faster/more disks (ext2 with noatime, btw) seemed
> like a good idea. :)
> ok, from what you're both saying, I might not have to worry
> about where to put the 5Gb partitions on these drives, but
> basically, it can't hurt.  I've been going on the assumption
> that the most important performance gains will come from 1)
> the xtra spindles, and 2) the better seek times on the 15K
> SCSI (versus 7200k SATA) drives.
>
> thanks,
> john
>
>
>

Chris
Received on Mon Sep 12 2005 - 11:55:29 MDT