Performance of PostgreSQL VM on local storage vs NFS

[tommisan]

Hi everyone,
I would like to virtualize a PostgreSQL database in production environment (KVM) and I would like to know if someone of you has been using it running on local disk (for example RAID 1 SAS, where Proxmox 3.3 is already installed) or NFS storage (or other storage solution..).
I read on the net that NFS solution should be avoided for consistency and performance issues.
I would like to have a feedback from you, thank you in advance,
tommisan

 

[WaltervdSchee]

For any serious production database, I'd only trust local storage (or iSCSI/ Fiber multipathed SAN), NFS is indeed simply not stable enough.
It can become unavailable, which will cause hanging I/O's , and timeouts. Also, the database relies on fsync's to keep the WAL logging and the database consistent, which are not guaranteed on NFS.

If you are running this for a tryout / test, then you can probably get away with it, meaning, it will work ... But again, WAL logging relies on guaranteed fsyncs ... (which is why its recommended to switch off disk based write caches)

 

[wahmed]

I agree that NFS may cause issue specially if there is no RAID redundancy. For one of our client we used Ceph as storage backend for SQL server which holds quite large database. It has been in operation for about 2 years now without any issue. I personally cringe when it comes to storing data on local storage.

 

[tommisan]

Thank you very much for your replies. I just bought "Mastering Proxmox", Ceph could be a good solution, I am going to read about it.
I don't like local storage too, but with a RAID 1, spare and physical backup I don't think it's so bad..