Date: Tue, 2 Sep 2014 16:07:45 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Borja Marcos" <borjam@sarenet.es> Cc: FreeBSD-scsi <freebsd-scsi@freebsd.org> Subject: Re: Samsung 840 Pro SSD and quirks Message-ID: <14D38CFE3887426D9065E26F50457F30@multiplay.co.uk> References: <A04E6D4A-907E-45AB-9668-0BF6827FD178@sarenet.es> <D8A848BC8761493EA5A049BFA77852CF@multiplay.co.uk> <93D764A8-01AE-42FA-8020-65CEB6C7D64C@sarenet.es>
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Thanks for the confirmation Borja I was a little confused why
our two results differed.
For a 12 disk system you'll likely need two SAS2 controllers,
or at least 12 SAS lines otherwise you will hit controller
throughput issues as a 840 can pretty much saturate a single
SAS2 lane on its own.
At that point you'll also start to see other issues.
I'd strongly suggest moving to stable/10, if you haven't already,
particularly if you have large amount of RAM in the system
otherwise you will become CPU bound on ARC hash lookups.
Regards
Steve
----- Original Message -----
From: "Borja Marcos" <borjam@sarenet.es>
To: "Steven Hartland" <killing@multiplay.co.uk>
Cc: "FreeBSD-scsi" <freebsd-scsi@freebsd.org>
Sent: Tuesday, September 02, 2014 3:48 PM
Subject: Re: Samsung 840 Pro SSD and quirks
On Sep 1, 2014, at 5:44 PM, Steven Hartland wrote:
> We saw a noticable performance increase on 4k on our 8TB 840
> array but I too couldn't find any concrete information either.
>
> If anyone has this info and can confirm either way that would
> be great.
I stand corrected. I have done some benchmarks with just two Samsung
SSDs (zpool with two disks, no mirroring) and indeed I get better
performance with 4 KB blocks.
I did my original tests with 12 disks and some other bottleneck was
hiding the performance difference.
In both cases, anyway, Trim was working unless the system lies.
Thanks!
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