Bad 3ware 9000 performance 5.4?

[Martin Nilsson]

Alexis Yushin wrote:
> 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