Re: [squid-users] about ufs and aufs

On Monday 06 August 2001 12:33 am, mani wrote:
> Thanks for your infromation. I need some further clarification..
>
> I have tested squid with 200 req/sec with enabling the aufs.But in cache
> log i am getting the warning "Queue congestion - Disk I/O" .
>
> How can I overcome this problem? how can we calculate the number of
> threads needed...?

This came up on the list just recently. It's caused by either the threads
falling too far behind squid or the disks falling too far behind the
threads.

How many threads are you working with?
I have found 8/IDE drive and 12/SCSI drive to work well, but YMMV,
especially since small drives tend to be slower, too.

Also, you don't give the specs (CPU, NIC, etc), but 200 req/s is a hefty
amount of real-world traffic. Even assuming that's peak, we're talking
12-15 millions hits/day. It's possible the IO backlog is from CPU
starvation or other bottlenecks.

        -- Brian

> RH7.1
> squid2.4STABLE1
> 512MB RAM,
> 3X5GB cache
>
> Thanks.
>
>
>
> ----- Original Message -----
> From: Brian <hiryuu@envisiongames.net>
> To: mani <balu_2003@yahoo.com>; <squid-users@squid-cache.org>
> Sent: Sunday, August 05, 2001 2:11 AM
> Subject: Re: [squid-users] about ufs and aufs
>
> > On Friday 03 August 2001 11:45 pm, mani wrote:
> > > Hi,
> > >
> > > What is the the difference between ufs and aufs. As I know both are
> > > file system of the squid.In ufs mode it handles the request as
> > > single processes but in case of aufs it handles the request in a
> > > multiprocesses.. am I correct here, if not educate me.
> >
> > Multiple threads. Threads are lightweight processes that share the
> > same memory space, making switches between them very fast. Squid also
> > has a multi-process storage system, diskd.
> >
> > > What is advantage and disadvantages of ufs mode? What we achieve
> > > when we go aufs..? How these both mode works..?
> >
> > Disk operations block the process making the request until the data is
> > available. In ufs, squid handles the io operations itself, which
> > means it blocks on disk IO and will not scale very far. In aufs,
> > squid hand the io operations off to other threads. Those threads
> > block, but the main squid continues normally.
> >
> > The problem with aufs is threads are not well supported (either by
> > squid or even the OS itself) on all systems. It also incurs some CPU
> > overhead from squid 'tending the flock' of threads.
> >
> > Redhat 7 should handle threads just fine, so use aufs if this squid
> > will be seeing a decent amount of traffic.
> >
> > -- Brian
>
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Received on Mon Aug 06 2001 - 01:16:54 MDT