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Date:      Wed, 23 Jan 2013 23:52:32 +0100 (CET)
From:      Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
To:        Steven Chamberlain <steven@pyro.eu.org>
Cc:        freebsd-fs <freebsd-fs@freebsd.org>, Mark Felder <feld@feld.me>, Chris Rees <utisoft@gmail.com>
Subject:   Re: ZFS regimen: scrub, scrub, scrub and scrub again.
Message-ID:  <alpine.BSF.2.00.1301232347110.2474@wojtek.tensor.gdynia.pl>
In-Reply-To: <510067DC.7030707@pyro.eu.org>
References:  <CACpH0Mf6sNb8JOsTzC%2BWSfQRB62%2BZn7VtzEnihEKmEV2aO2p%2Bw@mail.gmail.com> <alpine.BSF.2.00.1301211201570.9447@wojtek.tensor.gdynia.pl> <20130122073641.GH30633@server.rulingia.com> <alpine.BSF.2.00.1301232121430.1659@wojtek.tensor.gdynia.pl> <CADLo838Rst7wEtV7DpY23XjpcFCsOkrN=axE1AscyO7vYgSKSg@mail.gmail.com> <op.wrdudwx334t2sn@markf.office.supranet.net> <CAFqOu6gcvTEYCtLEUoyd4tX7acrk=V85u4EuNiDWVj4X%2B0Dcpg@mail.gmail.com> <alpine.BSF.2.00.1301232240200.2067@wojtek.tensor.gdynia.pl> <510067DC.7030707@pyro.eu.org>

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>> unless your work is serving movies it doesn't matter.
>
> That's why I find it really interesting the Netflix Open Connect
> appliance didn't use ZFS - it would have seemed perfect for that

"Seems perfect" only by ZFS marketers and their victims.
but is at most usable, but and dangerous.

> application.

because doing it with UFS is ACTUALLY perfect.
large parallel transfers are great with UFS, >95% of platter speed is 
normal and near zero CPU load, metadata amount are minimal and doesn't 
matter for performance and fsck time (but +J would make it even smaller).

Getting ca 90% of platter speed under multitasking load is possible with 
proper setup.

> http://lists.freebsd.org/pipermail/freebsd-stable/2012-June/068129.html
>
> Instead there are plain UFS+J filesystems on some 36 disks and no RAID -
> it tries to handle almost everything at the application layer instead.

this is exactly the kind of setup i would do in their case.
They can restore all data as master movie storage is not here.
but they have to restore 2 drives in case of 2 drives failing in the same 
time. not 36 :)

"application layer" is quite trivial - just store where each movie is.

such setup could easily handle 2 10Gb/s cards. Or more if load is spread 
over drives.



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