Re: degraded RAID performance after OS upgrade, and drives added.
On Nov 29, 2006, at 6:18 PM, Derrick MacPherson wrote: We updated to 6.1 this weekend and added 3 300gb drives to the external raid cabinet, they were to go on a seprate controller but the server happens to have a few other boxes on top making it impossible at that time, so we put the 3x300 (RAID5) , upgraded the OS and performance is very poor. When I run systat I see upward of 300 tps on the problematic array (da2) and under systat - vmstat : It's normal for RAID-5 to perform worse than a single drive-- and sometimes it performs much worse, as in nearly an order of magnitude slower, for the case of very small writes. If you value performance, choose another RAID level like RAID-0, RAID-1, or RAID-10. -- -Chuck ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
RE: degraded RAID performance after OS upgrade, and drives added.
That seems like a pretty crazy drop in performance, more than one would expect. The machine is busy but not busy enough to warrant this.. Imo.. Is there a way to test to confirm? -Original Message- From: Chuck Swiger [EMAIL PROTECTED] To: Derrick MacPherson [EMAIL PROTECTED] Cc: freebsd-questions@freebsd.org Sent: 11/30/06 10:39 Subject: Re: degraded RAID performance after OS upgrade, and drives added. On Nov 29, 2006, at 6:18 PM, Derrick MacPherson wrote: We updated to 6.1 this weekend and added 3 300gb drives to the external raid cabinet, they were to go on a seprate controller but the server happens to have a few other boxes on top making it impossible at that time, so we put the 3x300 (RAID5) , upgraded the OS and performance is very poor. When I run systat I see upward of 300 tps on the problematic array (da2) and under systat - vmstat : It's normal for RAID-5 to perform worse than a single drive-- and sometimes it performs much worse, as in nearly an order of magnitude slower, for the case of very small writes. If you value performance, choose another RAID level like RAID-0, RAID-1, or RAID-10. -- -Chuck ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: degraded RAID performance after OS upgrade, and drives added.
On Nov 30, 2006, at 11:40 AM, Derrick MacPherson wrote: That seems like a pretty crazy drop in performance, more than one would expect. The machine is busy but not busy enough to warrant this.. Imo.. Is there a way to test to confirm? Using dd is a trivial benchmark, and not especially precise but good enough to give rough answers; otherwise, there are lots of I/O benchmarks in ports like iozone or even diskinfo -t. Try using different block sizes while reading and writing with dd, and you'll probably find some useful info. While it is likely that you can adjust the RAID-5 stripe size, change the write-caching from write-thru to write-back (if your RAID has a battery, anyway, otherwise this is dangerous), etc, using a 3-disk RAID-5 volume is just not a great idea-- RAID-5 is happier with more drives than the minimum of 3 to get better parallelism and reduce the overhead for parity info. -- -Chuck ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to [EMAIL PROTECTED]
