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Subject: Re: Samsung 840 Pro SSD and quirks
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From: Borja Marcos <borjam@sarenet.es>
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Date: Tue, 2 Sep 2014 17:17:28 +0200
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To: "Steven Hartland" <killing@multiplay.co.uk>
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On Sep 2, 2014, at 5:07 PM, Steven Hartland wrote:

> Thanks for the confirmation Borja I was a little confused why
> our two results differed.

What do you use for your benchmarks? I am still playing with this, so I =
can run the same tests just in case.

I have done something pretty straightforward, just creating a pool, a =
dataset, and running bonnie++ on it. I also
have a backplane=20


>=20
> 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.
>=20
> At that point you'll also start to see other issues.
>=20
> 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.

Yes, I'm following -STABLE but this braindead machine has just *one* =
PCIe slot, so
I am limited to one controller. In my case, a SAS2008 (mps driver) with =
a SAS expander.=20

mps0: <LSI SAS2008> port 0x3f00-0x3fff mem =
0x90ebc000-0x90ebffff,0x912c0000-0x912fffff irq 32 at device 0.0 on =
pci17
mps0: Firmware: 18.00.00.00, Driver: 19.00.00.00-fbsd
mps0: IOCCapabilities: =
1285c<ScsiTaskFull,DiagTrace,SnapBuf,EEDP,TransRetry,EventReplay,HostDisc>=



Anyway, my main concern is not that maximum throughput, the system will =
be much faster than the  same using
"classic" hard disks :)




Borja.