Re: Disk Layout

In article <33FB110C.3646@bloomberg.com>, "Art S. Kagel" <kagel@bloomberg.com> writes >Steve Romankiw wrote: >> >> I have been unable to find information reguarding the pros & cons of >> RAID and ODS. >> >> We are running Sun Solaris 2.5.1 with VxVM and ODS 7.23 UC1. We >> planning for some expansive growth in our database(s). In our Sparc > >> Some of the questions I have are: >> >> Q: Should I simply create two partitions per drive? This creates two >> 2gb partitions which the max chunk size for ODS. >> >> Q: Should I employ RAID 0+1? Get the benefits of striping and >> mirroring? >> >> Q: Is your decision different based upon OLTP vs DSS? > >We have found the best performance from our DG Clariion RAID subsystems >by preparing a large stripe set from a large number of drives >each of which has been mirrored onto a drive on another Clariion >subsystem with separate controller and power supply. We use from 15, >20 & 30 drive stripe sets of 4 or 9 GB drives. DG firmware can then >divide the 260GB pseudo-physical drive into 130 2GB logical drives. We >then create a symbolic link to each of the raw devices in a single >directory and add these (or pieces of them for smaller DBs) as our >Informix chunks. > >Because of the wide stripe, the firmware level mirror, and the >controller level caching performance is beautiful. I stopped testing >with 100 processes pumping 30MB per second, total, out to the same >logical raw device and the last addition of 10 more processes gained 7% >increased throughput from the 11% increase in processes so there was >still a little more throughput to squeeze out (this was with 4GB drives >the 9GB drives rotate 30% faster so...). > >Obviously, if you do not need 270GB of storage you can adjust the stripe >size accordingly. The keys seem to be > 1) Stripe mirrored pairs so that the striping software can just write >to each stripe member and the mirror firmware can load balance the two >mirrors. > 2) Get intelligent RAID arrays with large caches which can be used >effectively for elevator sorting of writes. We added cached controllers >the the Clariions last year while still using RAID 5. Performance >improved dramatically (I/O waits reduced 75%) but the mirrors blow RAID >5 away for pure performance and are MUCH more reliable and yes 40% more >expensive. > >Hope this helps. > >Art S. Kagel Many drives?, large disk caches?, using TWO controllers in parallel for mirroring? I'm very jealous!! -- David Williams