[ale] Postgresql archive logs

[Lightner, Jeff]

Question:

For large (~1 TB) Postgresql DB is it better to have archive logs on same RAID set as the DB to maximize spindles for the DB or to setup two separate RAID sets thereby reducing spindles for the DB?

We currently have a Dell PowerEdge with PERC (LSI OEM) RAID Controller.   Initially it was setup with all 6 internal disks in the same RAID5 set.

Our DBAs believe that having archive logs on same disks as DB is a problem so want us to redo the layout so that we have 1 x 2 disk mirror for the OS and archive longs and a 1 x 4 disk RAID 5 for the DB.   This effectively reduces the spindles for DB from 6 to 4.   I’m wondering if the performance implications of such a reduction would outweigh the data integrity setup.

Please do NOT suggest installing more disks, or attaching to an external array.   These aren’t options for this system.   Also please don’t talk about the importance of doing backups I already know that.   Finally don’t talk about whether RAID 5 is a good idea – I already know the pitfalls.   My questions is not to talk about how it could be done better with more/different equipment but rather what is best with the equipment described above.









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