Date: Tue, 3 Nov 1998 16:25:15 -0600 From: Dan Nelson <dnelson@emsphone.com> To: Graeme Tait <graeme@echidna.com>, freebsd-questions@FreeBSD.ORG Subject: Re: File system performance Message-ID: <19981103162515.A17979@emsphone.com> In-Reply-To: <363F7AA3.22254A9C@echidna.com>; from "Graeme Tait" on Tue Nov 3 16:50:27 GMT 1998 References: <363F7AA3.22254A9C@echidna.com>
next in thread | previous in thread | raw e-mail | index | archive | help
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). When you say caching controller, do you mean that it's got a write cache? If so, then you're probably running your filesystem in the equivalent of async mode, which would explain the speed increase. > When deleting these files (rm -rf), the 486 does it with a minimum of > fuss (no trashing of the disk heads) at about 120 files a second. Disk > operations occur ever second or so with intervals between. Looks like a write cache to me. A single file deletion only writes a few parts of the disk, but it does it synchronously. So a thousand deletes in the same directory results in at least two thousand seeks, back and forth to the same couple disk blocks. Your caching controller is probably just caching the writes. 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. -Dan Nelson dnelson@emsphone.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?19981103162515.A17979>