IBM System Storage DS6000 Series: Copy Services in Open Environments

Appendix A. Open systems specifics 471

Copy Services limitations with Windows 2000 and Windows 2003

Having the drive information stored on the disk itself imposes some limitations when using

Copy Services functionality on a Windows system:

򐂰 The source and target volumes must be of the same physical size. Normally the target

volume can be bigger than the source volume; with Windows, this is not the case, for two

reasons:

– The LDM database holds information relating to the size of the volume. As this is

copied from the source to the target, if the target volume is a different size from the

source, then the database information is incorrect, and the host system returns an

exception.

– The LDM database is stored at the end of the volume. The copy process is a

track-by-track copy; unless the target is an identical size to the source, the database is

not at the end of the target volume.

򐂰 It is impossible to have the source and target FlashCopy volumes on the same Windows

system when they were created as Windows dynamic volumes. The reason is that each

dynamic volume has to have its own 128-bit GUID. As its name implies, the GUID must be

unique on one system. When you perform FlashCopy, the GUID gets copied as well, so

this means that if you tried to mount the source and target volume on the same host

system, you would have two volumes with exactly the same GUID. This is not allowed,

and you are not able to mount the target volume.

Copy Services with Windows volumes

In order to see target volumes on a second Windows host, you have to do the following:

1. Perform the Remote Mirror and Copy/FlashCopy function onto the target volume. Ensure

that when using Remote Mirror and Copy that the primary and secondary volumes were in

duplex mode, and that write I/O was ceased prior to terminating the copy pair relationship.

2. Reboot the host machine on which you want to mount the Copy Services target volume.

3. Right-click Open Computer Management, and then click Disk Management.

4. Find the disk that is associated with your volume. There are two

panes for each disk; the

left one should read Dynamic and Foreign. It is likely that no drive letter is associated to

that volume.

5. Right-click that pane, and select Import Foreign Disks. Select OK, then OK again. The

volume now has a drive letter assigned to it and is of Simple Layout and Dynamic Type.

You can read it and write to that volume.

When performing subsequent Remote Mirror and Copy/FlashCopies to the target volume, it is

unnecessary to perform a reboot, because the target volume is still known to the target

system. However, in order to detect any changes to the contents of the target volume, you

Note: When using Windows dynamic disks, remember that to read FlashCopy targets, if

the FlashCopy pair has been rescanned or if the server reading targets has been rebooted,

FlashCopy targets appear as

foreign disks to that server. Manual intervention is required

to reimport those disks and restore operation.

Tip: Disable the Fast-indexing option on the source disk; otherwise, operations to that

volume get cached to speed up disk access. However, this means that data is not flushed

from memory and the target disk might have copies of files and folders that were deleted

from the source system.