starting Fedora Server SIG
Les Mikesell
lesmikesell at gmail.com
Thu Nov 20 14:05:58 UTC 2008
Matej Cepl wrote:
> On 2008-11-20, 07:00 GMT, Les Mikesell wrote:
>> Maybe - but it isn't a real solution. You still have to deal
>> with identifying the device before and during the labeling
>> process. If you can do that, you didn't really need the label.
>
> Sorry, maybe I don't understand, but what's so difficult on the
> following?
>
> tune2fs -l /dev/sda1 |awk '/UUID/ {print $3}'
>
The disk may be unformatted at this point and not have a UUID. Or if it
has filesystems, they may be types that don't support labels or UUID's
(vfat, etc.). But the point is that if you already knew it was
/dev/sda1, why do you need to care about anything else?
There are at least two different use cases here. One is that you have a
single machine where you move a known small set of drives around to
different positions (or they are usb/firewire, etc. where you don't have
a concept of position) and you always want the same partition mounted in
the same place regardless of where it ends up in the physical order. I
do have a machine like that and understand why the concept of labels or
uuids is useful - but in that case I made all of the partitions into
raid1 md devices (some mirrored, some with the 2nd member specified as
'missing' which accomplishes the same thing and lets me plug in a disk
with a matching partition and make a backup by adding it to the raid.
The other use case is where you have a large number of servers with
swappable drives and regularly swap them around. Scsi/sca backplanes
are usually predictable as to drive ordering so if you physically insert
a disk you automatically know the /dev/sd? name for it. This may not be
true for newer sas/sata controllers with raid logic that hides the
physical drives behind 'volumes' even if you configure one drive per
volume, though. But in any case you need a way to discover and identify
devices before and during the partitioning and filesystem creation
steps, and labels can't help you then.
--
Les Mikesell
lesmikesell at gmail.com
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