Re: Finding the Bottleneck
Maybe a local caching nameserver will help here as well.
(Just a quick though.)
Rich Puhek <firstname.lastname@example.org> 7 Jun 2001, at 22:47:
> By the way,
> In addition to checking the disk usage, memory, and the other
> suggestions that have come up on the list, have you looked at DNS?
> Quite often you'll find that DNS lookups are severely limiting the
> performance of something like a mailing list. Make sure that the mail
> server itself isn't running a DNS server. Make sure you've got one or
> two DNS servers in close proximity to the mail server. Make sure that
> the DNS server process isn't swapping on the DNS servers (for the kind
> of traffic you're pushing through, you may need a pentium class
> machine with 128 MB of RAM as your DNS server. Also, if possible, I
> like to have the DNS server I'm querying kept free from being the
> authoratative server for any domains (not always practical in a real
> life situation, I know).
> Also, there are probably some optimizations you can do for queue sort
> order. I'm most familiar with Sendmail, not qmail, so I don't know the
> exact settings, but try to process the queue according to recipient
> domain. That way, you gain some advantages with holding SMTP
> connections open to a server, rather than closing and reopening a
> session, etc.
> Jason Lim wrote:
> > Hi all,
> > I was wondering if there is a way to find out what/where the
> > bottleneck of a large mail server is.
> > A client is running a huge mail server that we set up for them
> > (running qmail), but performance seems to be limited somewhere.
> > Qmail has already been optimized as far as it can go (big-todo
> > patch, large concurrency patch, etc.).
> > We're thinking one of the Hard Disks may be the main bottleneck (the
> > mail queue is already on a seperate disk on a seperate IDE channel
> > from other disks). Is there any way to find out how "utilized" the
> > IDE channel/hard disk is, or how hard it is going? Seems that right
> > now the only way we really know is by looking at the light on the
> > server case (how technical ;-) ). Must be a better way...
> > The bottleneck wouldn't be bandwidth... it is definately with the
> > server. Perhaps the CPU or kernel is the bottleneck (load average:
> > 4.84, 3.94, 3.88, going up to 5 or 6 during heavy mailing)? Is that
> > normal for a large mail server? We haven't run such a large mail
> > server before (anywhere between 500k to 1M per day so far,
> > increasing each day), so ANY tips and pointers would be greatly
> > appreciated. We've already been playing around with hdparm to see if
> > we can tweak the disks, but doesn't seem to help much. Maybe some
> > cache settings we can fiddle with? Maybe the mail queue disk could
> > use a different file cache setting (each email being from 1K to 10K
> > on average)?
> > Thanks in advance!
> > Sincerely,
> > Jason
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