On Thu, Jan 16, 2014 at 6:34 AM, Alban Hertroys <haram...@gmail.com> wrote:
> On 16 January 2014 12:09, Achilleas Mantzios > <ach...@matrix.gatewaynet.com> wrote: > > http://www.unix-experience.fr/2013/2451/ > > > > FreeBSD is also a very mature platform for ZFS/postgresql. > > More mature than on Linux even, as far as I know. If I had to choose > an OS to use ZFS with, I'd go with > either FreeBSD or Solaris. That said, I am biased to FreeBSD anyway; > the only Linux installation that I > own is the one in my Android phone, while I own several FreeBSD systems. > > > On Thu, Jan 16, 2014 at 4:22 AM, Sébastien Lorion < > s...@thestrangefactory.com> > > wrote: > >> > >> Hello, > >> > >> Since ZFS on Linux (http://zfsonlinux.org/) has been declared > production > >> ready last March (v0.6.1), I am curious if anyone is using it with > >> PostgreSQL on production servers (either main or backup) and if so, > what is > >> their experience so far ? > >> > >> Thank you, > >> > >> Sébastien > > I do not consider ZFS an ideal file-system for databases. I'm not an > expert on ZFS, but there are two > features in ZFS that I think particularly make it less suitable for > database use. > > One reason is that ZFS, as I understand it, is a log-structured > file-system. That means that changes to files always > go to the end of the file-system. If that file is a large frequently > updated database table, records are going to be far > apart and in fairly random order. That could seriously hurt performance. > > Secondly, with ZFS you need to reserve a significant amount of memory > for the ZIL. That is memory that is > not available to your database. > > Don't take my word for it, but I think the above points are worth > investigating as is finding some file-system bench- > marks where ZFS gets compared to, for example, UFS2 (FreeBSD), Ext4fs > (Linux). > Of course, the other side of the coin is ZFS's excellent flexibility. > > Cheers, > > Alban Hertroys > -- > If you can't see the forest for the trees, > Cut the trees and you'll see there is no forest. > > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general Those are very good points, but from my own tests and recent TPC benchmarks I saw on the net (sorry, don't have the links anymore), using SSD makes them not/less an issue. As you say, ZFS flexibility and ease of maintenance trumps many cards. Also, something worth pointing out and which may be counter-intuitive is that using ZFS compression can actually speed things up: http://citusdata.com/blog/64-zfs-compression Sébastien
