Re: Sarge Performance

From: Roberto C. Sanchez (roberto_at_familiasanchez.net)
Date: 05/21/05

  • Next message: Almut Behrens: "Re: customizing PS1 environment var with colour escape codes breaks readline" 
    Date: Sat, 21 May 2005 16:41:35 -0400
To: debian-user@lists.debian.org

    Lars Roland wrote:
    > Hi all
    >
    > I just replaced my company anti-virus/anti-spam mail gateway from a
    > Redhat 7.3 with kernel 2.4.24 to Debian Sarge with kernel 2.6.8.1. I
    > had hoped that this transition would lead to better performance (new
    > perl, better drivers in the kernel and so on) but the performance has
    > instead drooped about 30%.
    >
    > Here is my setup.
    >
    > Hardware:
    > IBM 335 with dual 2.4 Ghz Xeon, 1GB Ram and 1 10.000RPM SCSI disk.
    >
    >
    > Software:
    >
    > Minimal Debian Sarge (that is I have turned all unnecessary services off).
    > Kernel 2.6.8.1-SMP.
    > Reiserfs on all file systems.
    > Qmail MTA configured with up to 70 incoming connections.
    > ClamAV running as a daemon.
    > 10 Spamassassin daemons (spamd)
    > Qmail-scanner.
    >
    > On my old Redhat systems the hardware could scan around 60.000 emails
    > pr. hour with an average scan time of 5.6 seconds (including time from
    > both ClamAV and Spamassassin) and average load of 23.7.
    >
    > My new Sarge installation on the same hardware scans 40.000 emails pr
    > hour with an average scan time of 4.8 but with a load average of 57.8.
    >
    > Interestingly if i time the internal handling of the email then Sarge
    > seams to win.
    >
    > 1) Unpacking the email with Ripmime is about 5% faster than the old
    > Redhat system.
    > 2) Spam scanning the email is about 10% faster than the old Redhat system.
    > 3) Perl handling of the email is about 2% faster.
    > 4) ClamAv is scanning 4% faster.
    >
    > (the above numbers is the average taken from 4 days of mail flow
    > (about 3.9 million emails))
    >
    > This fact leads me to think that the system cannot handle as many
    > emails as before because it simply does not handle enough connections
    > (eg. the connections time out on the SMTP port before even getting to
    > the scanners) - To persue this idea I have tried the folowing
    >
    > 1) Change the file system to XFS, EXT3.
    > 2) Running Reisefs with notail, nodiratime and noatime
    > 3) Renice qmail-smtpd so it gets higher priority than spamd (hoping
    > that this would lead to more connections getting handled).
    > 4) Change the I/O scheduler to deadline (elevator=deadline).
    > 5) Changed the kernel to 2.4.
    > 6) Turning the firewall (iptables) completely off.
    >
    > Non of it has worked. And yes I do get 60.000 incoming connections pr.
    > hour most of them just seams to time out an get handled by the next MX
    > in my DNS.
    >
    > To see if the server could take the load on its own I have tried
    > changing my MX to only contain this one server. This made the load
    > jump to 98.9 and then the server eventually died with around 55
    > defunct perl process's floating around - my old Rehat server could
    > handle being the only mail server just fine (with loadavg around
    > 28.5).
    >
    > So as it is now I am a bit baffled by the slowness of Sarge, because
    > all the other systems I have converted to Sarge and kernel 2.6 have
    > run significantly faster (Database servers, web servers, name
    > servers...).
    >
    > So my question is this, does anyone know of any limitation in Sarge
    > (default values of incoming connections (not that I have ever heard of
    > such a thing)) that would cause my system to degrade in a way that it
    > has. When I do a telnet to port 25 I simply do not get a connection
    > fast enough (most of them times out) so this leads my to suspect that
    > something is wrong.

    Not sure. It appears that you have covered your bases pretty
    well in terms figuring out where the bottleneck might be. I
    would recommend reposting on debian-isp, since there are likely
    people there that are more accustomed to dealing with extremely
    high-volume mail servers. At least, you are more likely to
    find someone there than here.

    -Roberto 

    -- 
Roberto C. Sanchez
http://familiasanchez.net/~sanchezr



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