Peter,
What version(s) of VMS are you using? As Jan said, any version of VMS .ge. 7.2 can handle extended bitmaps, which will let you use a cluster size of 8 on a 1 TB disk (or 4 on a 512 GB disk or 2 on 256 GB disk or 1 on a 128GB disk.) So just the fact that you are using ODS2 is not an issue, as long as you are using VMS 7.2 or higher.
LDDRIVER and DFU are two utilities that in my opinion should be on every VMS system. There were plans at one time to include them as supported software, but the those plans changed. Both tools were written by Digital employees as internal tools, and then made available on the freeware CDs. Now they are available from Jur's site
http://www.digiater.nlIf you use LD devices, it is possible to have all "disks" used by a server on a single LUN, but there are less complications if you can use one for the system disk, and one for your user partitions (LD devices). For example it makes it much easier to backup just the system disk when upgrading.
If you are going to use writable LD devices, and you don't want the disks to be rebuilt every time the system reboots, you will need to make sure they get dismounted before the device their container file is on. In other words if lda101 has its containter file on $1$dga2, then lda101 should be dismounted (and ideally disconnected) before $1$dga2 is dismounted.
Unfortunately, sys$system:shutdown.com does not have a user callout for dismounting disks. The SYSHUTDWN.COM can do this, but this is executed prior to user processes being stopped and the removal of installed images, so either you need to put all that logic in your SYSHUTDWN.COM, or modify SYS$SYSTEM:SHUTDOWN.COM to do the dismounts or to callout to a command procedure of yours that will. Be aware that it is at least possible to create LD devices on other LD devices (like the cat in a hat), so if you want to be absolutely sure that devices are dismounted in the correct order, you will need to parse the output of $ ld show /all or write a program to do something similar.
We have an EVA, so the only thing I normally use LD devices for is to emulate CD-ROM devices. The LD devices can be write protected and saved in metadata in the container file header, so even if the device is mounted without the /nowrite qualifier, the disk will still be mounted write-locked (just like a real CD-ROM device would behave). For disks that are mounted /nowrite, you don't need to worry about the order in which the devices are dismounted.
Here's an example of nested LD devices (just for demonstration, I don't recommend doing this)
$ pipe free | search/nowin sys$pipe lda ! free is Hunter Goatley's FREE disk space
$4$LDA101: LEVEL1 50344 (51%) 49656 (49%) 100000
$4$LDA102: LEVEL2 25329 (51%) 24671 (49%) 50000
$4$LDA103: LEVEL3 221 ( 1%) 24779 (99%) 25000
$ ld show /all
%LD-I-CONNECTED, Connected _$4$LDA101: to $1$DGA2210:[000000_LD_DSK]LEVEL1.DSK;1
%LD-I-CONNECTED, Connected _$4$LDA102: to $4$LDA101:[000000_LD_DSK]LEVEL2.DSK;1
%LD-I-CONNECTED, Connected _$4$LDA103: to $4$LDA102:[000000_LD_DSK]LEVEL3.DSK;1
$
For these to be cleanly dismounted, you must first dismount and preferably disconnect the disk that has no active container files on it, in this case $4$lda103:, then $4$lda102, then finally $4$lda101:
LD devices work fine in a cluster, but there is nothing analogous to the configure process to automatically create the devices on other cluster nodes. LD devices can not be MSCP served, but if the device that their container file is created on is MSCP served, it has the same effect.
To create LD devices clusterwide, you can do something like the following:
$ mcr sysman set environment/cluster
SYSMAN> set profile /priv=all
SYSMAN> do ld connect $1$DGA2210:[000000_LD_DSK]LEVEL1.DSK lda101 /share
SYSMAN> do mount/system lda101 level1
SYSMAN> do ld connect $4$LDA101:[000000_LD_DSK]LEVEL2.DSK lda102 /share
SYSMAN> do mount/system lda102 level2
SYSMAN> do ld connect $4$LDA102:[000000_LD_DSK]LEVEL3.DSK lda103 /share
SYSMAN> do mount/system lda103 level3
SYSMAN> exit
I think you will find that LD devices are well worth the effort to learn to use them. They are extremely useful for testing, and when extra features like tracing are not active, they have low overhead as well.
Jon
it depends
