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Re: using a NetBSD host as an iSCSI target for OSX (time machine) (or other mechanisms)
On Nov 16, 2009, at 1:52 PM, Andy Ruhl wrote:
On Mon, Nov 16, 2009 at 2:32 PM, Chuck Swiger <cswiger%mac.com@localhost> wrote:
alive. Using RAID-1/5/6 storage based upon multiple disks, which can
withstand single-drive failure without losing data, is a good idea;
alternatively, you can also backup a TM storage volume onto tape or
to obtain more robust backups.
I'll have to learn about Mac tape support, if it exists. I have some
tape drives I could try. I'd have to attach them through a scsi to USB
converter I suppose.
I admit that I'm used to native tape drive support via a device node
such as /dev/nsa0 or /dev/rmt/0ubn which you can point tar or dump/
restore at; evidently, in the Mac world, tape drive support comes from
third-parties such as Dantz/EMC Retrospect, which seems to be the de-
facto backup software shipped with Mac tape drives.
YMMV; I used DLT and sDLT tape drives with Legato Networker on Sun
boxen for more than a decade with completely satisfactory results--
ie, users could browse for stuff they wanted to restore, and the
sysadmins would get requests to put in specific tapes if the current
backup tape(s) (one client even forked out for a 7-tape autoloader)
didn't have the needed contents; and we never encountered a failure to
restore data-- but it seems that LTO and AIT are taking over, nowadays.
Althogh attaching a RAID disk or tape drive by USB just seems wrong
to me on some level.
Yes, you should use Firewire or SCSI by preference, or maybe Fibre
Channel for higher-end roles. USB requires fairly constant support
from the host CPU to keep data flowing (somewhat akin to PIO mode in
ATA); Firewire/SCSI/Fibre controllers have enough brains to handle DMA
to or from memory for themselves without constantly grabbing the CPU
to move bytes around.
Something like a 40GB AIT drive here:
...claims to be supported by Retrospect. Caveat: I have dubious views
upon the older 4mm DDS helical scan tape mechanisms; the tapes were
fragile and easily damaged, and it was an open question whether a tape
written by one drive could be read by another model, or even another
drive which was the exact same model that wrote the tape.
8mm AIT cartridges are supposed to be better, but I'd prefer a linear
format like sDLT or LTO given a choice....
[ ... ]
I'm probably paranoid.
IMHO, you can't possibly be too paranoid where backups are concerned.
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