Have you done any experiments implementing RAID 50 this way (HBA does RAID 5, OS does RAID 0)? If so, what were the
results?
Ron
-----Original Message-----
>From: Scott Marlowe <smarlowe@g2switchworks.com>
>Sent: Jul 18, 2006 3:37 PM
>To: Alex Turner <armtuk@gmail.com>
>Cc: Luke Lonergan <llonergan@greenplum.com>, Mikael Carneholm <Mikael.Carneholm@wirelesscar.com>, Ron Peacetree
<rjpeace@earthlink.net>,pgsql-performance@postgresql.org
>Subject: Re: [PERFORM] RAID stripe size question
>
>On Tue, 2006-07-18 at 14:27, Alex Turner wrote:
>> This is a great testament to the fact that very often software RAID
>> will seriously outperform hardware RAID because the OS guys who
>> implemented it took the time to do it right, as compared with some
>> controller manufacturers who seem to think it's okay to provided
>> sub-standard performance.
>>
>> Based on the bonnie++ numbers comming back from your array, I would
>> also encourage you to evaluate software RAID, as you might see
>> significantly better performance as a result. RAID 10 is also a good
>> candidate as it's not so heavy on the cache and CPU as RAID 5.
>
>Also, consider testing a mix, where your hardware RAID controller does
>the mirroring and the OS stripes ((R)AID 0) over the top of it. I've
>gotten good performance from mediocre hardware cards doing this. It has
>the advantage of still being able to use the battery backed cache and
>its instant fsync while not relying on some cards that have issues
>layering RAID layers one atop the other.