Re: ZFS filesystem - supported ? - Mailing list pgsql-general

On Saturday, October 23rd, 2021 at 14:03, Mladen Gogala <gogala.mladen@gmail.com> wrote:

> On 10/23/21 07:29, Laura Smith wrote:
>
> > Hi,
> >
> > Given an upcoming server upgrade, I'm contemplating moving away from XFS to ZFS (specifically the ZoL flavour via
Debian11). BTRFS seems to be falling away (e.g. with Redhat deprecating it etc.), hence my preference for ZFS. 
> >
> > However, somewhere in the back of my mind I seem to have a recollection of reading about what could be described as
a"strong encouragement" to stick with more traditional options such as ext4 or xfs. 
> >
> > A brief search of the docs for "xfs" didn't come up with anything, hence the question here.
> >
> > Thanks !
> >
> > Laura
>
> Hi Laura,
>
> May I ask why would you like to change file systems? Probably because of
>
> the snapshot capability? However, ZFS performance leaves much to be
>
> desired. Please see the following article:
>
> https://www.phoronix.com/scan.php?page=article&item=ubuntu1910-ext4-zfs&num=1
>
> This is relatively new, from 2019. On the page 3 there are tests with
>
> SQLite, Cassandra and RocksDB. Ext4 is much faster in all of them.
>
> Finally, there is another article about relational databases and ZFS:
>
> https://blog.docbert.org/oracle-on-zfs/
>
> In other words, I would test very thoroughly because your performance is
>
> likely to suffer. As for the supported part, that's not a problem.
>
> Postgres supports all modern file systems. It uses Posix system calls to
>
> manipulate, read and write files. Furthermore, if you need snapshots,
>
> disk arrays like NetApp, Hitachi or EMC can always provide that.
>
> Regards
>
>
>
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Mladen Gogala
>
> Database Consultant
>
> Tel: (347) 321-1217
>
> https://dbwhisperer.wordpress.com

Hi Mladen,

Yes indeed, snapshots is the primary reason, closely followed by zfssend/receive.

I'm no stranger to using LVM snapshots with ext4/xfs but it requires a custom shell script to manage the whole process
aroundbackups.  I feel the whole thing could well be a lot cleaner with zfs. 

Thank you for the links, I will take a look.

Laura