Joshua Baker-LePain jlb17@duke.edu wrote:
I guess it depens on your definition of "trouble". These are benchmarks I ran on this system with the 2 3wares in hardware RAID5 and a software RAID0 across them: write read ----- ---- ext2 81 180 ext3 34 222 XFS 109 213 That ext3 write speed was something I just wasn't willing to live with on a system that used to perform so much
better
(running RH7.3, hw RAID, and XFS).
That's because the 3Ware Escalade 7000-8000 series only have 1-4MB of SRAM. The Ext3 journal logic is rather "dumb" (especially on old kernel 2.4) and bursts _more_ than 4MB at a time. As a result, you overflow the small SRAM cache of the 7000-8000 series, and the XOR stalls.
Newer Ext3 journaling code in newer 2.4/2.6 kernels is a little better, but I still do _not_ recommend you use RAID-5 on the 7000/8000 series. I have repeatedly recommended RAID-10 for 3Ware Escalade 7000-8000 series.
I'm still holding off on recommending the 3Ware Escalade 9500S for RAID-5, although most people are seeing good performance with the 9.2.1.1 firmware released ~9 months ago. The verdict is still out on the far newer 9550SX series (with PowerPC).
Lastly, and quite repeatedly, the 3Ware card does _not_ offer hot-swap capability when you use JBOD modes. I, among countless others, have been saying this for years. You have to use _another_ kernel facility to "hide" the status of the discs when you're using JBOD modes.