Date: Tue, 03 Nov 1998 19:01:39 -0500 From: Graeme Tait <graeme@echidna.com> To: Dan Nelson <dnelson@emsphone.com> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: File system performance Message-ID: <363F9963.EFF480F4@echidna.com> References: <363F7AA3.22254A9C@echidna.com> <19981103162515.A17979@emsphone.com>
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Sorry - should have done this before sending my last reply, but I didn't think I'd have time tonight to do this test. The Senegal Ballet beckons ... . Dan Nelson wrote: > > In the last episode (Nov 03), Graeme Tait said: > > I have a situation that involves manipulating large numbers of small > > files of about 1k each. I recently noticed a strange performance > > comparison between my "play" system (a 486-DX2/66/16MB with > > run-of-the-mill IDE drives and a Promise caching controller, running > > 2.2.6R) and "production" system (Pentium-II/400/256MB with Ultra 2 LVD > > SCSI and 4.5GB Seagate Cheetah drives, running 2.2.7S/CAM). <snip> > Try rerunning the test on both systems with your filesystems mounted in > async mode, and see how the numbers change on both systems. Consider > whether this type of activity is all that common on a production > machine. If it is (and your machine is stable enough), you might want > to run in async mode all the time, or upgrade to 3.0 and use > softupdates instead. Wow! - the "production" system is over ***50*** times faster at file deletion with the file system mounted async. I'd be willing to trade my first born for that sort of improvement. The disk heads are still very busy, but obviously in a much more efficient way. I do notice that it seems to withhold the final writes for about 2 seconds (as does the Promise hardware cache). Is this behaviour controllable? Is the data withheld, if lost (as in a power outage or crash) just mean the disk data is erroneous, or would there be serious filesystem damage? -- Graeme To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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