Re: Write disk image to multiple drives


Grant wrote:
On 28 Feb 2006 18:49:28 -0800, "Phil" <phillip.paradis@xxxxxxxxx> wrote:

unfortunately the images aren't simply gzip'd; they're in a format used

Yes but the final image _is_ available in non compressed form, use
a written CF unit as master.

That works as well. Though an additional benefit of using Frisbee is
that it only writes allocated sectors to the card; the filesystem uses
only about half of the available space on the card, so the time savings
there are significant. (Especially since CF isn't all that fast at
writing.) Also, the eventual end-users of the system aren't that
bright; they might stick an blank in the source slot...

If those USB channels are not independent, you may not see much
of a win in running things in parallel, USB is serial comms, you're
hoping to fill one CF's busy time writing to others over serial
communications?

Our primary writer station is using 16 writers; 8 per bank. Each bank
is connected to a separate root hub on the host system. Each bank
consists of 8 writers, a 7 port hub and a 4 port hub. 6 writers are
connected to the 7 port hub along with the 4 port hub; the remaining
two writers are connected to the 4 port. I just finished assembling the
system the other day and haven't had a chance to test it with 16 cards,
but the prototype system (4 writers on a single hub) showed little
difference between writing a single card and writing 4 cards; USB2 is
much faster than the maximum write speed of the cards. I suspect
writing 8 cards on one channel will be a bit slower, but still much
faster than writing them sequentially.

An update: I figured out how to get hald to stop automounting the cards
if they've been previously formatted (also breaks automouting of CDs,
floppies and memory sticks, but it's a dedicated machine and I don't
much care...I found a sample .fdi file in the docs folder that disables
mounting of hotplugged block devices) and hacked the script to filter
partition devices. (partition block devices are subfolders of their
parent device in sysfs; they don't have their own folder in /sys/block.
Adding the following in my loop works.

[ -d /sys/block/$device ] || continue

Of course, if anyone knows a cleaner solution (e.g. preventing udev
from creating the symlinks to the partition nodes in the first place
and/or stopping the kernel from reading the partition table and
generating hotplug events for the partitions) I'm all ears.

Cheers,

--
Phil

.

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