Hi,
Running FreeBSD 5.4... three machines with twe/3ware 8000 and three twa/ 3ware 9500-8 controllers. All of them running RAID 1+0 without write cache since we dont have battery backup unit. All of them Seagate 7200 SATA. I get about 46Mb/s write on the 8000 series and only 5(!)MB/s on the 9500 series.
I have noticed that the MegaRAID SATA cards sometimes disables the write cache on Seagate SATA drives, resulting in a write performance of about 6MB/s. Can you check if the 3ware also does this. I have had arrays were only one disk had write cache disabled and it totally ruined the performance of the whole array.
As always be sure to have a good UPS if you are using write cache on the disks! With the sad state of todays ATA/SATA disks turning of write caching in the drive is often not an option.
/Martin
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