Dear Managers,
I am trying to figure out if adding additional
disk to an existing raidset (shows up as one disk to the
host, "unpartitioned" in Infortrend jargon).
details:
The raid system we are using (Infortrend 3101) allows the following
general configuration.
You can have upto two drive channels (upto 15 scsi drives on each) and
you may form upto 8 raid sets (infortrend calls these logical drives) which
can further be split into 8 units that appear to the host as individual
scsi drives.
My current configuration is as follows:
I have 5 (4.5G) disks forming one raid set (raid 5), and it is not split further.
So the host sees a 18G disk. It is further partitioned in the traditional
unix manner using disk label (rrz0a through rrz0h).
I'd like to add another disk to the ensemble, and I'd like to add it
without destroying existing data. I seem to have the following
options -
(I know that LSM will eliminate lot of the headaches, but for
reasons beyond my control, LSM is not an option for me here).
1. Add the disk in, and put it in its own raid set (or in infortrend speak,
"logical drive" in JBOD (1 disk) config, and let the host see it
as a physical drive.
pros: easiest. least risky. eventually can add additonal disks and make
it a raid-5 as well.
cons: loses the reliability that comes with raid-5.
2. Add the disk and expand the raid set (if it doesnt destroy the existing
data). Partition the set into two "lun"s so the host will see
2 physical drives on the host channel.
pros: easy. uses existing raid-5.
cons: some doubt about data being destroyed when the set is expanded.
3. Add the disk into the existing set, expand it, and STILL assign additional
storage to the existing LUN. The host will still see only one
physical disk, only larger. (the set will still have one larger
"partition").
pros: uses existing raid. conserves one scsi id.
cons: High level of doubt about having the data destroyed when the "apparent"
disk is made larger.
My emails to infortrend went unanswered. My highest priority is to
avoid destriying the data. (we do have backups but cant afford the
downtime).
Ideally, I like to do either #2 or #3. In situation #2,
does the extra space appear at the end of the (unsplit) raid set
that can simply be peeled away to make a second LUN?
Similarly, in situation #3, how is the larger disk going
to look like to the host? Does it show up with the extra blocks
at the end, and would it simply be a matter of editing the disklabel
to get an unused partition (eg: /dev/rrz0d which wasnt being used
before) to contain the expanded space?
Thanks in advance!
-vijay
Received on Mon Dec 20 1999 - 22:01:47 NZDT