Re: RAID stripe size question

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(at)g2switchworks(dot)com>
>Sent: Jul 18, 2006 3:37 PM
>To: Alex Turner <armtuk(at)gmail(dot)com>
>Cc: Luke Lonergan <llonergan(at)greenplum(dot)com>, Mikael Carneholm <Mikael(dot)Carneholm(at)wirelesscar(dot)com>, Ron Peacetree <rjpeace(at)earthlink(dot)net>, pgsql-performance(at)postgresql(dot)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.