Date: Wed, 5 Mar 2014 09:28:49 +0000 From: krad <kraduk@gmail.com> To: Olav Gjerde <olav@backupbay.com> Cc: FreeBSD FS <freebsd-fs@freebsd.org> Subject: Re: Is LZ4 compression of the ZFS L2ARC available in any RELEASE/STABLE? Message-ID: <CALfReyc6hwc13TFc8AGZbVvyK2enfEjhJ8ndAAQ6p7pWzg-QCg@mail.gmail.com> In-Reply-To: <CAJ7kQyEp208XKt3CaiBufiB%2Bg_CHAkUgzAzVdX_6Gx2WyW1ENg@mail.gmail.com> References: <CAJ7kQyGTOuynOoLukXbP2E6GPKRiBWx8_mLEchk90WDKO%2Bo-SA@mail.gmail.com> <53157CC2.8080107@FreeBSD.org> <CAJ7kQyGQjf_WbY64bLVX=YfmJUfAd8i22kVbVhZhEWPMg7bbQw@mail.gmail.com> <5315D446.3040701@freebsd.org> <CAJ7kQyFf19Un_TS=kW=T21HT%2BoabhsUhJij5oixQ2_uh0LvHRA@mail.gmail.com> <alpine.GSO.2.01.1403042037290.1717@freddy.simplesystems.org> <CAJ7kQyEp208XKt3CaiBufiB%2Bg_CHAkUgzAzVdX_6Gx2WyW1ENg@mail.gmail.com>
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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@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 h= as > 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@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 database= s > >> related to running PostgreSQL on ZFS. Which is why I'm so interested i= n > >> 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 mor= e > > data may be read than needed, and likewise, writes may result in writin= g > > far more data than needed. > > > > Regardless, L2ARC on SSD is a very good idea for this case. > > > > Bob > > -- > > Bob Friesenhahn > > bfriesen@simple.dallas.tx.us, > http://www.simplesystems.org/users/bfriesen/ > > GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ > > > > > > -- > Olav Gr=F8n=E5s Gjerde > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" >
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