Imaging mounted disk volumes under duress

Re:Imaging mounted disk volumes under duress by makr17 on Tuesday September 21, 2021 @06:34PM (#28610869)

Definitely possible on Linux. In the not distant past I had a large on-prem PostgreSQL DB that had a hot standby that we used for backups. Since ZFS snapshots are atomic you can just snapshot the dataset under the DB without worrying about quiescing the database. And then zfs send backups to files that are then backed up offsite.

If you ever cared it's easy enough to clone one of those snapshots and bring it up as another DB instance to poke around at how things used to be...

[ Parent | on HN ]

Re:Imaging mounted disk volumes under duress by ryanmjacobs on Tuesday September 21, 2021 @08:08PM (#28611627)

I've been doing this with several production PostgreSQL instances.

PostgreSQL on ZFS is great.

I have zstd compression enabled and I average 3.50x compression ratios.

(Probably some pretty awful CPU tradeoffs in there, but system load and query times seem fine. My database is 50 GB before zstd compression, so enabling it helps a ton.)

I also have ZFS snapshots taken hourly and shipped offsite. It's awesome that I don't need to pause PostgreSQL or anything to take the snapshot. It's atomic and instant.

[ Parent | on HN ]

Re:Imaging mounted disk volumes under duress by donavanm on Wednesday September 22, 2021 @05:47AM (#28614585)

With some quick and dirty `time` style tests zstd has a pretty low overhead. IIRC writing was around off = 100, lz4 = 110, zstd = 115 cpu utilization on my personal data set that resulted in 1x, 1.7x, 2.1x compression. Reading was negligible, single digit percentages, for both lz4 & zstd. For anything on a spindle that's a pretty good trade off of CPU time.

[ Parent | on HN ]