Forum OpenACS Q&A: Re: OT: Dell PowerEdge RAID 10 Configuration

Posted by James Thornton on
Andrew - Yes, the client's dev server has everything on a RAID 1 volume and the Postgres data is on an ext3 (journaling) file system. There are several things I can do to improve performance, and one would be to move the Postgres data to a non-journaling FS. In this case moving the DB data to a separate disk would also improve performance, but the SAME paper argues that segmenting data on separate disks isn't the most practical way to take advantage of all available disks and is prone to individual disks becoming bottlenecks.

Another technique to minimize disk head movement suggested in the SAME paper is to partition disks so that frequently accessed data is stored on the outer half of the disks where the read time is lower. It says, "positioning data at a very fine level to reduce seek time does not help much, and "it is enough to position data that is accessed frequently roughly in the same half or quarter of a disk drive"; however, I am curious as to how Postgres organizes/groups its data. For example, is it grouped together on the disk, or is it prone to be spread out over the disk? Does vacuum reorganize the data?