We're running on EBS volumes on EC2. We're interested in leveraging EBS snapshotting for backups. However, does this mean we'd need to ensure our pg_xlog is on the same EBS volume as our data?

(I believe) the usual reasoning for separating pg_xlog onto a separate volume is for performance. However, if they are on different volumes, the snapshots may be out of sync.

1 Answer 1


Having the transaction log (pg_xlog) on separate storage can increase write performance on most RDBMS platforms. If yours is a (concurrent) write heavy application, you may see a performance benefit.

If the snapshots are not synchronous however, you could lose data from uncomitted transactions in the event of an unclean restart. I suppose in certain situations a pg_resetxlog could be required after a failure.

You could look into WAL archiving, or even techniques similar to ZFS snapshotting if EBS snapshots have the same effective purpose.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.