Is LZ4 compression of the ZFS L2ARC available in any RELEASE/STABLE?

[krad]

I thought the recordsize referred to the maximum block size rather than the
actual block size. Please correct me if im wrong


On 5 March 2014 07:17, Olav Gjerde <olav at backupbay.com> wrote:

> Currently I've set the recordsize to 8k, however I'm thinking maybe a
> recordsize of 4k may more optimal?
> This is because the compressratio with LZ4 is around 2.5 and this value has
> been constant for all my data while growing from a few megabytes to a
> tenfold of gigabytes.
> Maybe something I should play with to see if it makes a difference.
>
>
> On Wed, Mar 5, 2014 at 3:40 AM, Bob Friesenhahn <
> bfriesen at simple.dallas.tx.us> wrote:
>
> > On Tue, 4 Mar 2014, Olav Gjerde wrote:
> >
> >  I managed to mess up who I replied to and Matthew replied back with a
> good
> >> answer which I think didn't reach the mailing list.
> >>
> >> I actually have a problem with query performance in one of my databases
> >> related to running PostgreSQL on ZFS. Which is why I'm so interested in
> >> compression for the L2ARC Cache. The problem is random IO read were
> >> creating a report were I aggregate 75000 rows takes 30 minutes!!! The
> >> table
> >> that I query has 400 million rows though.
> >> The dataset easily fit in memory, so if I run the same query again it
> >> takes
> >> less than a second.
> >>
> >
> > Make sure that your database is on a filesystem with zfs block-size
> > matching the database block-size (rather than 128K).  Otherwise far more
> > data may be read than needed, and likewise, writes may result in writing
> > far more data than needed.
> >
> > Regardless, L2ARC on SSD is a very good idea for this case.
> >
> > Bob
> > --
> > Bob Friesenhahn
> > bfriesen at simple.dallas.tx.us,
> http://www.simplesystems.org/users/bfriesen/
> > GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
> >
>
>
>
> --
> Olav Grønås Gjerde
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