FreeBSD 11.1 Beta 2 ZFS performance degradation on SSDs

[Caza, Aaron]

> -----Original Message-----
> From: Karl Denninger [mailto:karl at denninger.net]
> Sent: Monday, June 19, 2017 7:28 PM
> To: freebsd-fs at freebsd.org
> Subject: Re: FreeBSD 11.1 Beta 2 ZFS performance degradation on SSDs
>
> Just one note below...
>
> On 6/19/2017 19:57, Caza, Aaron wrote:
> >
> > Note that file /testdb/test is 16GB, twice the size of ram available in this system.  The /testdb directory is a ZFS file system with recordsize=8k, chosen as ultimately it's intended to host a PostgreSQL database which uses an 8k page size.
> Do not make this assumption blindly.  Yes, I know the docs say to set
> recordsize=8k but this is something you need to benchmark against your
> actual working data set.
>
> MANY Postgres workloads are MUCH faster (2x or more!) if you use a
> default page size and lz4 compression -- including one I have in
> production and have extensively benchmarked.  The difference is NOT small.
>....
>
> zroot/ticker  compressratio         1.53x                         -
> zroot/ticker  mounted               yes                           -
> zroot/ticker  quota                 none                          default
> zroot/ticker  reservation           none                          default
> zroot/ticker  recordsize            128K                          default
> zroot/ticker  mountpoint            /usr/local/pgsql/data-ticker  local
> zroot/ticker  sharenfs              off                           default
> zroot/ticker  checksum              fletcher4
> inherited from zroot
> zroot/ticker  compression           lz4
> inherited from zroot
> zroot/ticker  atime                 off
> inherited from zroot
>
> You may also want to consider setting logbias=throughput.  In some cases
> the improvement there can be quite material as well -- depending on the
> insert/update traffic to the database in question.
>
> --
> Karl Denninger
> karl at denninger.net <mailto:karl at denninger.net>
> /The Market Ticker/
> /[S/MIME encrypted email preferred]/

Thanks for the suggestions Karl.  I'll investigate further after I resolve this performance degradation issue I'm experiencing.  I recently read another FreeBSD+ZFS+PostgreSQL user's Scale15x presentation, PostgreZFS, Sean Chittenden if I recall correctly, who also advised lz4 compression + 16K page size rather than 8K with PostgreZFS.

With regards to my performance woes, I was originally using PostgreSQL in my posts to freebsd-hackers at freebsd.org but started using 'dd' to remove it as a point of contention.  In attempting to resolve this issue, I tried using your patch to PR 187594 (https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=187594).  Took a bit of effort to find a revision of FreeBSD 10 Stable to which your FreeBSD10 patch would both apply and compile cleanly; however, it didn't resolve the issue I'm experiencing.

--
Aaron


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