Mirrors for Moving Partitions

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Draft

This article captures some instructions that have previously been posted in the oes-nw-storage-media forum.

Why use mirroring for moving?

Sometimes it is desirable to have a partition contiuously online even when being moved to a new storage device. Netware's native mirroring (now called RAID1 in NSS documentation and in the NSSMU command) can help with that. The mirroring process is done in the background while the system is actively accessible.

Some other migration strategies may have short down times equivalent to how long it takes to run a backup on the volumes on the partition in question. The down-time associated with these other methods has decreased, but mirroring may still be a helpful choice.

Note that mirroring can only be done on one system at a time, although the partitions can be moved to other systems later.

Should you want to learn more about using other methods, refer to your backup/restore documentation or investigate the Migration Wizard's Volume Consolidation Utility. The article at Migration Wizard is not VCU-oriented, but some of the tuning steps may be helpful.

A recent thread that had an interesting need for mirroring was from a system administrator who was expanding his pool, attempting to create a new partition on his hardware RAID5 storage. Due to a selection issue, the new partition was actually created on local storage. If the partition is added to the pool before this is realized, it can be a bit awkward (as well as unsafe -- spanning a pool across devices should never be done without hardware RAID support, since losing any partition loses the whole pool). In this case, mirroring the one partition to the RAID5 storage takes care of that issue. Since mirroring is done at the partition level, and not at the pool level, only the one partition needs to be mirrored.


Instructions

Mirroring the old storage to the new storage

The author's recommendation is as follows (see also mirroring threads in oes-nw-storage-media):

1) as always, have a working backup [e.g., on tape].

2) Go about installing the new disk [For external devices, make the connection -- plug in the cable or enable access in the array manager][For internal drives, shutdown first and reboot afterwards]

3) load NSSMU

4) Select DEVICES, and scroll down to the new device.

5) Press F3 to initialize it

6) return to top level menu and select RAID devices

7) select the partition of interest

8) Press F3 to expand the mirror

9) Select the new device from the popup list.

10) Press F5 occasionally if you want to see the mirror percentage update, otherwise exit.


Removing the Old Storage

1) as always, have a working backup [e.g., on tape].

2) Pull the bad disk out of the system. [if this is a SAN device, you can probably do this with the system up by pulling a cable or by setting it "offline" in the array manager] [for internal drives, you'd shutdown first, and reboot afterwards]

3) load NSSMU

4) Select DEVICES

5) Press F2 to scan devices

6) return to the main NSSMU menu

7) Select RAID devices

8) Select the RAID (mirror) set of interest

9) Select the "offline" partition

10) Press the DELETE key

11) You now have a "complete" mirror, even if it only has 1 partition in it.

Notes

There might be an initial peformance bump when you start the mirroring process, but there's a set parameter that can be used to throttle it ("Concurrent Remirror Requests" under the "Disks" category). The author's experience is that loads are generally uuder 5% (and often under 2%) during mirroring with FC HBAs.

For NW6.5 NRM, "Partition Disks" is in the left column, rather than on the volumes page.

For breaking a mirror, the author prefers NSSMU, btw. NRM on NW6 may not handle the choice of partitions correctly; NW6.5 looks a bit better, though.

For breaking the mirror, there used to be a "this will delete all data" warning, the author hasn't seen that now in a recent version of NSSMU.

The only way to preserve the old copy is to disconnect it before breaking the mirror; the OS can't wipe the partition when it is "offline".

Comparing the NRM and NSSMU methods

From NRM: select "Volumes" from the left column, select "Disk Partitions" from the resulting display. Find the new device, and click the "Initialize Partition Table" link. Find the old device, and the partition holding VOL1, and click the "mirror" link. In the page that takes you to, select the new device. Go get a cup of coffee (or a pot, depending on how much data you have to mirror). When the mirroring is complete, click on the "100% mirrored" link, select the old partition, and click on "remove this partition from the mirror group", and if the prompt looks good, answer yes.

From NSSMU: select DEVICES, then scroll down to the new device, and press F3. Answer Y. ESC to get back to the main menu, select PARTITIONS, then scroll down to the old partition, and press F3. Select the new device from the Free Space list. Go get a cup of coffee (or a pot, depending on how much data you have to mirror). When the mirroring is complete, ESC to the main menu and select RAID DEVICES. Select the "device" with VOL1, then select the raid segment that is on the old device, and press DEL. Exit NSSMU.

References

OES2 NSS Documentation:

Managing Software RAID Devices

TID 10096727: How to expand an existing volume with NSS in NetWare

TID for expanding volumes

TID 3776107: How To Clean Up The Software Raid After Deleting It From NSSMU

Partfix of mirrors

This TID recommended by Tim Heywood seems to allow you to get rid of the "mirror of size 1 partition" if that bothers you.

Various screen shots of NSSMU:

Devices
Partitions
Partition Info
RAID Devices
RAID Info
Pools
Volume Properties

Room for Corrections

Looking forward to the sysops' notes on this page.