Um, he said from the Raptor TO an array, which means the array is writing.
Oh yes, so he did, my bad. Very interesting this is then! So how could you tell the Raptor was the bottleneck? And did you take into any controller cache? I'm quite interested in this.
I said I was transferring FROM his Raptor UNTO the array. So the Raptor Reads and the RAID5 writes. And yes, I do not recommend 3 disk RAID5, but 5 disk RAID5 should perform much better than any single drive (read or write) and also beat a two disk RAID0. You don't need 10-15 disk arrays to have decent performance. If your experience is different, something else bottlenecks your system (controller, bus, blocksize etc.)
Are you
sure you're taking into account the drive cache? I find write speeds are lightning fast until the cache fills up and then things slow down considerably as the disk subsystem strains to keep up.
I don't find the increased risk of RAID0 acceptable. Systems should be reliable first, fast second. Do you always remember to backup your desktop, every day/week? Anyway, I don't ever recommend RAID0.
Well, personally I have a network filesystem available and I make sure that I write all data I want to keep on that. But an automated routine is perfectly adequate, where's the hardship in scheduling a backup routine or double clicking a desktop icon every so often to do a backup?
Whether a system should be reliable first or not depends on what the system is for!
I have serious doubts whether a 5 disk RAID 5 system will beat two disk RAID 0 for write performance. For pete's sake it's all on the original post. This guy has 2 disks in RAID 0 and it was lightning fast and then had 3 disk RAID 5 and it was dog slow. Same hardware, different setup, and it's slower, that's what you'll get with any controller. RAID 0 will beat RAID 5, I challenge you to find some statistics or benchmarks that say otherwise!
Here's some sources that highlight the poor performance of RAID 5.
http://www.dbazine.com/datawarehouse/dw-articles/rittman8:
"RAID 5 can severely affect performance on highly updated databases."
http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96533/iodesign.htm
When describing RAID 5:
"Sequential reads benefit the most, while write performance can suffer."
"Recent RAID 5 implementations avoid many of the traditional RAID 5 limits by installing large amounts of battery-backed memory (NVRAM)."
http://www.oracle-base.com/articles/misc/RAID.php?display_type=printable
This documents recommends the use of combinations of RAID 0 and RAID 1 over RAID 5 in all cases except where money needs to be saved.
http://www.dba-oracle.com/oracle_tips_raid5_bad.htm
Finally this documents highlights the flaws of RAID 5 for database performance and highlights that the recent advance that makes RAID5 viable in such situations is the onboard cache
And here's one more I added after my original post from Wikipedia
http://en.wikipedia.org/wiki/Raid_5#RAID_5
This just gives a general good overview about what I've been saying. In particular the RAID 5 Performance section backs up what I've been saying that whilst RAID 5 read performance is decent, "almost as good as RAID 0 for the same number of disks," the write performance is poor.