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Date: Thu, 14 Jul 2011 17:54:58 -0400 (EDT)
From: Justin Piszcz <jpiszcz@lucidpixels.com>
To: linux-kernel@vger.kernel.org
cc: Alan Piszcz <ap@solarrain.com>
Subject: 2.6.39.2: discard not supported on mpt2sas
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Hi,

Something interesting to note:

When I have an Intel 510 SSD plugged into an mpt2sas board, discard (TRIM) 
is not supported:

[   16.483409] EXT4-fs (sda2): re-mounted. Opts: discard
[   17.814743] EXT4-fs warning (device sda2): 
release_blocks_on_commit:2679: discard not supported, disabling

With a regular SATA port or an (PCI-e 2.0 x1 card), it works but with the 
overhead, PCI-e x1 seems to peak around 400-430MiB/s for reads, whereas 
with an X8 SAS controller I see 480-495MiB/s as the benchmarks show on 
various websites, ah well, its one thing or the other.

Justin.