On 2/20/2012 5:34 AM, John McKown wrote:
On Mon, 2012-02-20 at 08:42 +0100, R.S. wrote:
<snip>
What is cool is that SMS storage group. Usually users do not see the
volumes, they see dasd space. In case of shortage you can simply add
some volumes to the group. You can even buy new box and simply add it to
the group. And that's really cool IMHO.
You'd like LVM2 on Linux. You assign your physical disk partitions to a
physical volume group (conceptually like an SMS volume group). You can
then divvy up the space in that group into various sized logical
volumes. This is then initialized with a filesystem with mkfs
(equivalent to ICKDSF, I guess). If the filesystem runs out of space,
and you used the proper type of filesystem (there are many), you simply
expand the size of the logical volume into unused space in the group.
You then resize the filesystem. If you used ext4 or btrfs, I think you
can do this while it is in use. If you used ext3, I think you need to
unmount it (take it "offline") to resize it. If you're out of space in
the volume group, buy another disk and initialize it into the physical
volume group, then expand. logical volume space does not need to be
physically contiguous.
We use LVM on Linux for System z. Unfortunately, it can't handle physical disks
that dynamically "grow" in size. :-(
On z/OS, we have two options for enlarging the space available in an SMS storage
group: a) we can define new volumes and add them to the group or b) we can
dynamically increase the size of the volumes already in the group. We have used
the latter approach many times because device addresses are at a premium here,
fewer, larger volumes are easier for us to manage, and we don't have to mess
with the z/OS IODF, IOCDS, SCDS/ACDS, etc. The new space is just "magically"
available.
To "grow" LVM physical volumes in Linux for z (RHEL6) we had to one-by-one
"drain" (pvmove) the volumes to be resized, remove from LVM, vary offline,
dynamically "grow", vary online, reformat and add back to LVM. If not enough
free space is available in the LVM group to hold the contents of one physical
volume, you must temporarily add another appropriately-sized volume to the group
before beginning this process and then remove it at the end. Whew! It was so
involved that the last time we had a Linux on z space issue, we bit the bullet
and just added a new physical volume to the LVM group (after first updating the
IODF/IOCDS). :-(
--
Edward E Jaffe
Phoenix Software International, Inc
831 Parkview Drive North
El Segundo, CA 90245
310-338-0400 x318
[email protected]
http://www.phoenixsoftware.com/
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to [email protected] with the message: INFO IBM-MAIN
