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Date: Tue, 18 Oct 2011 11:55:25 -0400
From: Gary Palmer <gpalmer@freebsd.org>
To: Patrick Donnelly <batrick@batbytes.com>
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Cc: freebsd-fs@freebsd.org
Subject: Re: [ZFS] Using SSD with partitions
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On Mon, Oct 17, 2011 at 11:53:43PM -0400, Patrick Donnelly wrote:
> Since people have asked about more details for my system:
> 
> It uses old desktop hardware with 5 1TB WD Caviar Blues in a raidz
> configuration with 1 of those drives being a hot spare (4 1TB drives
> in the raidz). The system currently has 2 GB of RAM IIRC.
> 
> I've been using NFS to access the data on my home network which has
> worked pretty well. Writing to NFS over my VPN from across the country
> is really bad which is one of the reasons I wanted to use a SSD for a
> ZIL. read/write performance overall tends to be bad though so I don't
> really know how much it will help. After fiddling around with NFS
> settings for a long time I soon gave up and instead use SSH when
> outside a LAN. That's another matter though and off-topic. :)

Block access protocols (NFS, CIFS) suck over anything other than a LAN.
If you think about it you basically have (and yes, this is WAY over
simplified but it illustrates the point)

Client: request block 0 of file 1
Server: block 0
Client: request block 1 of file 1
Server: block 1

So for each block (whether its 512 bytes, 4k or larger is irrelevant)
you spend most of your time waiting for the request to transit the
network.  You spend very little time actually sending or receiving data.

You're probably better off with something like WebDAV or the like as
they are less impacted by RTT issues as they request the entire file
at once.

Gary