Samsung 840 Pro SSD and quirks

[Steven Hartland]

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 at sarenet.es>
To: "Steven Hartland" <killing at multiplay.co.uk>
Cc: "FreeBSD-scsi" <freebsd-scsi at 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!