tweaking FreeBSD for Squid using

[Michael Conlen]

A lot of what you face doing a Squid server is backplane and other bus
issues, though it's dependant on what you call "high performance"

A pair of Sun E220R's (2 SPARC II processors) for example handled 1 million
requests a day on a pair of mirrored 72 GB drives each. (Granted they were
very nice 72GB drives). The thing about the Sun boxes was that they could
get information out of memory really really fast, and the NIC cards could
work to their full potential. Every device that did IO was on it's own PCI
bus. 

It used to be that IDE drives took more processing power from the host to
perform it's operations, where as SCSI does not. If that's still true I'd
use that as a reason to stay away from IDE. 

The other advantage of SCSI, if you need great disk IO, is that you can have
a lot of spindles. On a large SCSI system in a Sun for example I can get a
single drive array to look like one SCSI device (with 14 disks in it) and
put a lot of arrays on a channel. If I buy small, fast SCSI disks I can take
full advantage of the 160 MB/sec array, where as I've seen a big fast IDE
disk push no more than 10 MB/sec. The arrays can do RAID before it gets to
the controller card, so you don't need the RAID in the box at all. 

Speaking of which, does anyone know of SCSI disk arrays with hardware RAID
that work with FreeBSD? 

I've moved out of the Sun world and in to the FreeBSD world professionally
and have no idea what's out there for PC hardware.

--
Michael Conlen


-----Original Message-----
From: owner-freebsd-performance at freebsd.org
[mailto:owner-freebsd-performance at freebsd.org] On Behalf Of Alain Fauconnet
Sent: Tuesday, April 15, 2003 10:49 PM
To: Jason Stone
Cc: freebsd-performance at freebsd.org
Subject: Re: tweaking FreeBSD for Squid using

On Tue, Apr 15, 2003 at 07:31:24PM -0700, Jason Stone wrote:
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> 
> 
> > You didn't mention whether is it SCSI or IDE.
> 
> Based on the fact that it's 15k rpms, I'm guessing scsi - do ide disks
> faster than 7.2k rpms exist?

I don't know. Seems that IDE disks evolve too fast  for  me  nowadays.
That's also why I was writing that I'm  not  even  sure  that  the  old
stance "don't use IDE for servers" is still valid.
OOTH,  I've  had  a lot of trouble  with  busy  IDE-based  (ASUS  P4* m/b)
FreeBSD servers lately (hard hangs, see bug kern/44867).

> 
> 
> > Don't  do  RAID. Bring up a filesystem on each disk (with soft updates
> > of  course),  mount  them  "-o  noatime"  and  configure  Squid to use
> > multiple cache dirs.
> 
> Why is this preferrable to striping with raid-0?

Well, because Squid does load balancing over multiple cache dirs quite
well by itself, and (presumably) in a smarter way than just  spreading
raw disk blocks, so adding another layer of software for RAID-0 doesn't
bring anything, and wastes CPU cycles. I'm not even sure that hardware
RAID-0 is a good idea. According to my own experience (admittedly on a
Linux  box),  removing software striping and using multiple cache dirs
on  physical  volumes  gave  me  a  significant  performance boost and
lowered   the   load   average   of   the   server   by   about   30%.
Since then, I've always stayed away from RAID on Squid boxes, whatever
the O/S.

Er. This is getting off topic  maybe.  I'll  follow  up  privately  if
needed.

_Alain_
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