Re[2]: [CentOS] 3ware disk failure -> hang -- how does software RAID "hide" a disk?

-- Best regards, Mickael mailto:mikelists@silverservers.com Friday, January 6, 2006, 12:29:51 PM, you wrote: > Joshua Baker-LePain jlb17@duke.edu wrote: >> But, as the archives of this list will attest to, using > these >> boards in hardware RAID mode in centos 4 is bad news. >> Performance sucks. > At RAID-5 writes? Of course on the 7000/8000 designs. They > only have 1-4MB of SRAM, not enough to buffer SRAM. > Furthermore, software RAID-0 is _always_ going to be faster > than hardware RAID-0. RAID-5 reads are basically RAID-0 > reads (minus one stripe). > But at RAID-1 or RAID-10, 3Ware's 7000/8000 Storage Switch > designs are very, very fast. >> There's some sort of nasty interaction between the 3wares > and >> ext3 which makes the combo unusable, really. > Huh? _Never_ heard of that. I'm using 7000/8000 series > cards on RHEL3 and RHEL4 (as well as FC1-FC3), *0* issues. > All Ext3 filesystems. >> Hotplug worked just fine on this system when I tested >> (multiple times) via 'mdadm -f -r' and 'mdadm -a'. It's > the >> actual disk failure handling that's at fault here. > Yes, that's ... tada ... hotplug! > You can't just have a fixed disk "remove itself" from the OS. > That's causing your panic. > When you're using 3Ware in JBOD, all it can do is report the > disk failure and report the fixed disk as unusable and remove > it from the system. So for software RAID, it's up to the > _kernel_ to handle that right. > And sure enough, it doesn't. > Has absolutely nothing to do with 3Ware's card. When you use > JBOD and you remove or lose a disk, which is its own volume, > the 3Ware removes the volume -- just as if a "regular" ATA or > SCSI card with a disk. > There is no way for 3Ware to "hide" the volume or continue > using it -- because there is a 1:1 disc:volume relationship. > They only way to "hide" the disk is to use its hardware RAID > features, where multiple disks are a volume. > Until the kernel has standard, trusted features to handle > failed disks, it's the reason why I refuse to use software > RAID-1, 10 or 5. Hotplug in 2.6 is supposed to handle this > when setup correctly, but I've yet to see it.