"Bryan J. Smith" <thebs413 at earthlink.net> wrote: > Hold on a second ... > Are you using a SCSI backplane? > If so, that's the difference right there! ;-> > SCSI backplanes and host adapters work very, very different > on transient (or failure for that matter) than _any_ ATA or > regular SCSI (without a backplane). > They are still formulating similarly for SATA, and there > are some SCSI adopted standards for SATA backplanes. > But with SAS, much of that is becoming moot. > Okay, now things make far more sense. ;-> Okay, let me put this summary out ... 1) Software RAID with SCSI If you want reliable software RAID for failed drives or hot-swap drives, you want to get a host adapter _and_ a SCSI backplane that work together. The card must then have full SCSI-2 support via their driver for the SCSI subsystem to enable such disconnect and hot-swap features, which is then paired with the backplane hardware. 2) Hardware RAID with ATA 3Ware Escalade, Areca ARC and other ATA RAID controllers use _true_ hardware RAID by the way of ASIC or microcontrollers that _never_ let the OS see the "raw" disc. When the discs are managed into arrays, the on-board intelligence can handle failures and hot-swaps. If the discs are not managed as arrays, they report the discs as they are to the OS, which means if they fail or are removed, you'll _lose_ the device. Although these card's drivers might load via the SCSI subsystem, they are _not_ SCSI cards, and do _not_ have a full SCSI-2 feature set. 3) Software RAID with ATA, SCSI (non-backplane) or JBOD modes You're on your own here. If there is not a full SCSI-2 driver for your controller, with associated hardware to handle loss or transient, then you're likely going to get a panic. The "new option" in kernel 2.6 is allegedly hotswap, but I have never configured a storage device for it -- other than USB, FireWire, CompactFlash, etc... Now does this make more sense? ;-> -- Bryan J. Smith Professional, Technical Annoyance b.j.smith at ieee.org http://thebs413.blogspot.com ---------------------------------------------------- *** Speed doesn't kill, difference in speed does ***