I'm no drive expert, but it seems to me that our write performance is excellent. I think what most are concerned about is OLTP where you are doing heavy write _and_ heavy read performance at the same time.
Our system is mostly read during the day, but we do a full system update everynight that is all writes, and it's very fast compared to the smaller SCSI system we moved off of. Nearly a 6x spead improvement, as fast as 900 rows/sec with a 48 byte record, one row per transaction.
I've started with SATA in a multi-read/multi-write environment. While it ran pretty good with 1 thread writing, the addition of a 2nd thread (whether reading or writing) would cause exponential slowdowns.
I suffered through this for a week and then switched to SCSI. Single threaded performance was pretty similar but with the advanced command queueing SCSI has, I was able to do multiple reads/writes simultaneously with only a small performance hit for each thread.
Perhaps having a SATA caching raid controller might help this situation. I don't know. It's pretty hard justifying buying a $$$ 3ware controller just to test it when you could spend the same money on SCSI and have a guarantee it'll work good under multi-IO scenarios.
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