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Re: [K12OSN] Server Tuning



Have you tried using iostat? You can find it in the  sysstat rpm.

iostat <interval in sec> 
gives you really great, humanly understandable, data on your disk subsys.

My reading from your description  is that a single drive  isn't adequate to
keep up with the demands.  iostat should show that.

We run up to 60 (usu.30) concurrent smb sessions, about 10 - 20 afpd and
between 100 and 200 nfs sessions concurrently on 866MHz PIII machines w 512MB
RAM.  The big difference is that we run software raid 5 for home across 4 or 5
disks. The sw RAID adds some CPU load peaking to 10-15% --easily managed by
the generally low CPU demands on a file server.

I'd suggest another disk or two and sw RAID /home across the bunch.


Owen O'Donovan
Technology Coordinator
Battlefords School Division

--
Open WebMail Project (http://openwebmail.org)


---------- Original Message -----------
From: linuxk12 mountainlake k12 mn us
To: k12osn redhat com
Sent: Tue, 19 Apr 2005 11:03:40 -0500
Subject: [K12OSN] Server Tuning

> I have a server that is getting bogged down and am wondering how I 
> can tune it for better performance.
> 
> Initially when I noticed response times slowing, I used "top" to
> see what was going on.  When load averages are over 3.0,
> sometimes 5.0 and greater, response time is very poor.  At the
> same time, top reported that the processor was 90% idle or better.
> 
> That led me wonder if there was an i/o bottleneck with the processor
> idling while waiting for disk accesses to be completed. I don't know
> how to check for that.
> 
> More recently I discovered "vmstat" and have been using that to monitor
> what is going on.  Swapping doesn't appear to be a major problem 
> ("si" and "so" are usually at zero), so more memory wouldn't help me 
> with respect to swapping.  Would more memory help for some other reason?
> 
> What vmstat did show is that context switching is getting out of hand
> during the times when the server appears overloaded.  Typically the
> "cs" numbers are in the 300-500 range when things are humming along
> nicely.  But something will push that number into the 1000's then the
> 10,000's and sometimes 100,000s and the box stalls out at that point,
> waiting for the backlog to clear.  I typically use "vmstat 5" to
> see five second data.
> 
> So, I'm wondering if there is something I can tune to fix this.  Are
> there other monitoring tools I can use to show that my tuning is helping
> things?  Failing a tuning solution, what do I need to do to ensure that
> a new server has enough power to overcome this problem?
> 
> These are the specifics on the server.  This is a Dell server running
> RedHat with kernel 2.4.18-3.  It is mostly a file server that 
> supports NFS, smb and netatalk (AppleTalk) for about 160 computers.  
> There are about 80 smb connections and 80 live NFS connections all 
> day long of which perhaps a third to half are actively transferring 
> data at the same time.
> 
> The same server also acts as an ldap database (for the OSX clients) and
> mail server (sendmail, spamassassin, imap).  Here is a count of some
> of these processes that are all running at the same time as reported
> by 'ps':
> 
>       5 identd
>       5 spamd
>       7 /var/openldap/libexec/slapd
>       8 [kjournald]
>       8 [nfsd]
>      20 imapd    --- this looks unusual!
>      22 /usr/sbin/afpd
>      36 smbd
> 
> >From /proc/cpuinfo:
> 
> vendor_id	: GenuineIntel
> cpu family	: 6
> model		: 11
> model name	: Intel(R) Pentium(R) III CPU family      1400MHz
> stepping	: 1
> cpu MHz		: 1396.496
> cache size	: 512 KB
> bogomips	: 2785.28
> 
> There are two SCSI drives formated as ext3 and the drive that sees
> most of the io is mounted like this:
> 
> /dev/sdb1 /home ext3 rw,data=writeback,usrquota 0 0
> 
> So obviously I am using user quotas.  I don't remember what "writeback"
> is doing for me.
> 
> Initially I was looking at performance issues to see if I should upgrade
> to a gigabit ether connection, but with the current performance 
> problems, it doesn't appear to be able to fill even a 100Mb pipe.
> 
> Any suggestions are welcome.  If I need to invest some dollars to fix
> this I will, but I want to spend them wisely.
> 
> --
> Jon Harder
> Technology Coordinator
> Mountain Lake Public School
> Mountain Lake, Minnesota
> 
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------- End of Original Message -------


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