5 messages in org.freebsd.freebsd-hackersRe: Odd RAID Performance Issue| From | Sent On | Attachments |
|---|---|---|
| Stephen Sanders | Feb 13, 2012 6:47 am | |
| Tom Evans | Feb 13, 2012 7:45 am | |
| Ivan Voras | Feb 13, 2012 8:51 am | |
| Steve Sanders | Mar 27, 2012 6:39 am | |
| Stephen Sanders | Mar 27, 2012 1:48 pm |
| Subject: | Re: Odd RAID Performance Issue | |
|---|---|---|
| From: | Ivan Voras (ivo...@freebsd.org) | |
| Date: | Feb 13, 2012 8:51:12 am | |
| List: | org.freebsd.freebsd-hackers | |
On 13/02/2012 15:48, Stephen Sanders wrote:
We've an application that logs data on one very large raid6 array and updates/accesses a database on another smaller raid5 array.
You would be better off with RAID10 for a database (or anything which does random IO).
Both arrays are connected to the same PCIe 3ware RAID controller. The system has 2 six core 3Ghz processors and 24 GB of RAM. The system is running FreeBSD 8.1.
Did you do any additional OS tuning? Do you use UFS or ZFS?
The problem we're encountering is that the disk subsystem appears to 'pause' periodically. It looks as if this is a result of disk read/write operations from the database array taking a very long time to complete (up to 8 sec).
You should be able to monitor this with "iostat -x 1" (or whatever number of seconds instead of "1") - the last three columns should tell you if the device(s) are extraordinarily busy, and the r/s and w/s columns should tell you what the real IOPS rate is. You should probably post a sample output from this command when the problem appears.