Date: Sun, 16 Oct 2005 19:01:22 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: Will Saxon <WillS@housing.ufl.edu> Cc: stable@freebsd.org Subject: Re: Disk 100% busy Message-ID: <20051017000122.GF21223@dan.emsphone.com> In-Reply-To: <0E972CEE334BFE4291CD07E056C76ED807738005@bragi.housing.ufl.edu> References: <0E972CEE334BFE4291CD07E056C76ED807738005@bragi.housing.ufl.edu>
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In the last episode (Oct 16), Will Saxon said: > I am trying to diagnose a problem whereby a virus scanner (clam > antivirus) is taking too long to scan attachments on a mail server. > We have an attachment limitation of 20MB and an attachment of 7-20MB > can take over 3 minutes to scan. This often causes the sending mail > server to timeout and resend the mail. > > In this case, my mail gateway is is a dual 3.06GHz Xeon with 1GB of > ram and 2 36GB 15krpm drives in a raid-1 on a smart array 6i (cciss) > controller. I am running FreeBSD 5.4-RELEASE-p1. > > Systat -vmstat reports the disk mirror is 100% busy at all times on > this machine, with an average of around 300 tps at 15KB/t. This seems > wrong to me, as these numbers are maintained even when the system > doesn't otherwise appear busy. We don't seem to be swamped by log > writes. How can I tell what's generating these disk writes? At the > moment the 100% disk utilization is the only thing I can see that > would cause the scanning delay. The machine overall is sluggish with > file operations. Are you swapping? Check either "vmstat 1" or top output. You can also tell top to display blocking I/O requests per process by hitting "m", then ask it to sort by I/O by hitting "ototal<enter>". -- Dan Nelson dnelson@allantgroup.com
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