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.
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