On Wednesday August 24, mirko.benz@xxxxxx wrote: > Hello, > > The RAID5 configuration is: 8 SATA disks, 8 port Marvel SATA PCI-X > controller chip (SuperMicro board), Dual Xeon, 1 GB RAM, stripe size > 64K, no spare disk. > > Measurements are performed to the ram md device with: > disktest -PT -T30 -h1 -K8 -B65536 -ID /dev/md0 > using the default stripe size (64K). 128K stripe size does not make a > real difference. May I suggest you try creating a filesystem on the device and doing tests in the filesystem? I have found the raw device slower that filesystem access before, and a quick test shows writing to the filesystem (ext3) is about 4 times as fast as writing to /dev/md1 on a 6 drive raid5 array. > > If Linux uses "stripe write" why is it so much slower than HW Raid? Is > it disabled by default? No, it is never disabled. However it can only work if raid5 gets a full stripe of data before being asked to flush that data. Writing to /dev/md0 directly may cause flushes too often. Does your application actually require writing to the raw device, or will you be using a filesystem? NeilBrown - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
