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@xxxxxxxxxxxxxxxxx> >Sent: Jul 18, 2006 3:37 PM >To: Alex Turner <armtuk@xxxxxxxxx> >Cc: Luke Lonergan <llonergan@xxxxxxxxxxxxx>, Mikael Carneholm <Mikael.Carneholm@xxxxxxxxxxxxxxx>, Ron Peacetree <rjpeace@xxxxxxxxxxxxx>, pgsql-performance@xxxxxxxxxxxxxx >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.
