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Date:      Tue, 22 Jan 2013 09:40:24 -0600
From:      Kevin Day <toasty@dragondata.com>
To:        Warren Block <wblock@wonkity.com>
Cc:        FreeBSD Filesystems <freebsd-fs@freebsd.org>, Scott Long <scottl@samsco.org>, wblock@freebsd.org
Subject:   Re: RFC: Suggesting ZFS "best practices" in FreeBSD
Message-ID:  <A196DCF7-B5C0-4EAB-960F-795D99A4B7F5@dragondata.com>
In-Reply-To: <alpine.BSF.2.00.1301220804530.61512@wonkity.com>
References:  <314B600D-E8E6-4300-B60F-33D5FA5A39CF@sarenet.es> <alpine.BSF.2.00.1301220804530.61512@wonkity.com>

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On Jan 22, 2013, at 9:12 AM, Warren Block <wblock@wonkity.com> wrote:
>=20
> I would like to see guidelines for at least two common scenarios:
>=20
> Multi-terabyte file server with multi-drive pool.

[=85]

> The first is easy with the defaults, but particular tuning could be =
beneficial.  And would be a good place to talk about NFS on ZFS, usage =
of SSDs, and so on.


I run ftpmirror.your.org, which is a 72 x 3TB drive ZFS server. It's a =
very busy server. It currently houses the only off-site backup of all of =
the Wikimedia projects(121TB), a full FreeBSD FTP mirror(1T), a full =
CentOS mirror,  all of FreeBSD-Archive(1.5TB), FreeBSD-CVS, etc. It's =
usually running between 100 and 1500mbps of ethernet traffic in/out of =
it. There are usually around 15 FTP connections, 20-50 HTTP connections, =
10 rsync connections and 1 or 2 CVS connections.=20

The only changes we've made that are ZFS specific are atime=3Doff and =
sync=3Ddisabled. Nothing we do uses atimes so disabling that cuts down =
on a ton of unnecessary writes. Disabling sync is okay here too - we're =
just mirroring stuff that's available elsewhere, so there's no threat of =
data loss. Other than some TCP tuning in sysctl.conf, this is running a =
totally stock kernel with no special settings.=20

I've looked at using an SSD for meta-data only caching, but it appears =
that we've got far more than 256GB of metadata here that's being =
accessed regularly (nearly every file is being stat'ed when rsync runs) =
so I'm guessing it's not going to be incredibly effective unless I buy a =
seriously large SSD.

If you have any specific questions I'm happy to answer though.

-- Kevin




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