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Subject: Re: Which RAID Controllers to pick/avoid?
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From: Royce Ausburn <royce.ml@inomial.com>
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Date: Sun, 6 Feb 2011 20:39:29 +1100
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> On Wed, Feb 2, 2011 at 7:00 PM, Craig Ringer
> <craig@postnewspapers.com.au> wrote:
>> Whatever RAID controller you get, make sure you have a battery backup
>> unit (BBU) installed so you can safely enable write-back caching.
>> Without that, you might as well use software RAID - it'll generally =
be
>> faster (and cheaper) than HW RAID w/o a BBU.
>=20
> Recently we had to pull our RAID controllers and go to plain SAS
> cards.  While random access dropped a bit, sequential throughput
> skyrocketed, saturating the 4 lane cable we use.    4x300Gb/s =3D
> 1200Gb/s or right around 1G of data a second off the array.  VERY
> impressive.


This is really surprising.  Software raid generally outperform hardware =
raid without BBU?  Why is that?  My company uses hardware raid quite a =
bit without BBU and have never thought to compare with software raid =3D/

Thanks!

--Royce=