Date: Wed, 17 Nov 1999 09:30:37 -0800 From: "Scott Hess" <scott@avantgo.com> To: <freebsd-fs@freebsd.org> Subject: vinum, MYSQL, and small transaction sizes. Message-ID: <166101bf3121$76518900$1e80000a@avantgo.com>
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I've been experimenting with vinum striping as a means of improving MYSQL performance, and am having some odd results. Running a particular workload and a particular set of disks, at overload iostat shows the disk doing about 185 tps, and about 8KB/t. When I run the workload on a 256k striped volume made up of two drives, I'm finding that each drive does about 95 tps. I've also run the tests with slower drives, which do 155 tps for the single-drive test, and 80 tps for the striped test. I didn't expect to double the tps of the entire system - but getting no increase at all seems very suspect. Based on the transaction sizes iostat is reporting, I have tried restriping with 8k stripes, which gives me about 105 tps per disk, which is marginally better. Going the other direction, with 1m stripes, gave the same results as for 256k stripes. In an attempt to isolate the problem, I tried cat'ing very large files in parallel. The files were large enough to not fit in memory, and I ran four cat commands at the same time on different files. I found that running them all from a single disk gave 380tps (24M/s), running 4 on one drive and 4 on the other gave 200tps (12M/s) for each drive, 400tps (24M/s) aggregate, and running them on a 256k volume striped across the disks gave 100tps (6M/s) for each drive, 200tps (12M/s) aggregate. Given past experience with the Linux md driver, I really really really suspect I'm missing something. But I couldn't tell you what. Running under FreeBSD3.3-RELEASE. Later, scott To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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