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Date:      Mon, 19 Jun 2017 20:27:50 -0500
From:      Karl Denninger <karl@denninger.net>
To:        freebsd-fs@freebsd.org
Subject:   Re: FreeBSD 11.1 Beta 2 ZFS performance degradation on SSDs
Message-ID:  <5033585e-591e-99b5-c14e-0c0fb70f63fb@denninger.net>
In-Reply-To: <431d958c658a408d8bfd4c574a565439@DM2PR58MB013.032d.mgd.msft.net>
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[-- Attachment #1 --]
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@denninger.net <mailto:karl@denninger.net>
/The Market Ticker/
/[S/MIME encrypted email preferred]/

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