Rick Troth wrote:
Rob said:
Linux identifies the volumes by address rather than label
...
Then Vic said (to John):
The filesystem labels are not visible until *after* the DASD driver
has made all the disks present. Rob is lamenting that the DASD driver
is unable to use VOLSER to map disk device to block node (i.e. we're not
able to do something like dasd=L0A201,L0A202,L0A203 on the kernel
command line). Well, maybe lamenting is the wrong word... :)
Interesting distinction.
Really, though, IBM VOLSER labels are no different conceptually
from EXT2 filesystem labels. The very presence of an IBM VOLSER
means one of several "filesystems" is on the DASD.
I was going to argue the point, and then I realised the phrase "DASD
driver."
The drives are identified before, possibly minutes or even hours before,
the filesystem.
The filesystem isn't recognised until its mounted, and until that time
there doesn't have to be a filesystem at all.
However, the DASD driver does, I presume, recognise partitions, and
there's no reason those can't be labelled when they're created.
Partitioning is in fact a crude filesystem.
Very.
Ye olde PC partition table is nothing more than a four file system.
Improvements led to "extended partitions", but it's still just a
flat filesystem with partition numbers instead of filenames.
TRUE, partitions are handled by a different layer in the kernel.
But don't let that decieve you!!
Bring the concept of partitioning to DASD, it is no less
a filesystem than it is in PC land or the Unix universe.
Apply "CDL" and you get up to three z/OS datasets ... files! ...
as partitions.
So IBM VOLSERs are operationally no different from EXT2 labels.
Gotta wonder what the MVS DASD filesystem driver does with VOLSERs.
CMS FS put the CMS minidisk label into the label space of VFS
(when it worked, but we've discussed that recently).
MVS? I don't recall anything in the way of device drivers as we
understand them in PCDOS or Linux.
--
Cheers
John
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