Date: Sat, 07 Feb 2009 14:08:13 +0100 From: Kris Kennaway <kris@FreeBSD.org> To: Tim Judd <tajudd@gmail.com> Cc: Yavuz <maslak@ihlas.net.tr>, freebsd-questions@freebsd.org Subject: Re: is there any way to increase disk performance ? Message-ID: <498D87BD.3040305@FreeBSD.org> In-Reply-To: <498A7F31.30206@gmail.com> References: <1E37AE87F15C4E34B6EB1002AADEB87A@desktop2002> <498A7F31.30206@gmail.com>
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Tim Judd wrote: > Yavuz wrote: >> I have freebsd7 (amd64 bit) and sata2 disk 7200 rpm. >> >> it's running mail server which has services like pop3,imap,smtp and >> webmail on this machine. >> >> When I type systat 1 -vmstat on command line, even I rarely see that >> disk usage hits 100%. >> I have no problem as ram and cpu. they is enough. >> >> is there any way to increase disk performance without causing any >> problem ? >> > > So in one second, the disk hits 100% utilization, weather it's reading > or writing data to disk. You said above that "I rarely see" -- so even > though, as a server, you're running slow spindles, you are doing pretty > good. > > I've no real experience with a site that's (for example) been > slashdotted, to test what is tolerable, and what's not. But as I > currently guess, an OVERALL average between 25% to 33% is about as much > as I would ever tax a server for CONSISTENT averages. > > So if you're seeing it rarely, such as when somebody hits webmail and > takes 1 second of constant disk read to serve the content, I'd be happy > there... > > I don't think you have a problem, when you put your concern into the > broader scope of 1 minute, 1 hour, 1 day or 1 week. It'll be very > difficult to never see 100% in 1 second no matter how powerful the > machine is. Make sure you understand that gstat's "%busy" column does not tell you how close to capacity your disk is, it tells you what % of time it is handling I/O. Since modern drives can have many commands queued at any given time, those are not the same thing. To understand whether your disk is overloaded, look at the ms/r and ms/w times. Kris
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