Migrate LVM-Striped raw volumes from old to new disks?

[Stuart Abramson_2]

We are replacing an old EMC 3930 with a new EMC DMX 1000S.

We want to parallel over, in case we have to back out. A backout position is essential.

So, we didn't even consider "pvmove", which doesn't provide an "operate in parallel for a week option".

We were going to add LVM mirrors to the LVs and then parallel for a week, and then remove the old PVs from the VG/LVs and have the new mirrors on the new PVs become the only PVs in VG, and thus be migrated.

Now we discover that you can't do LVM mirroring on HP-UX 10.20 on Striped LVs.

So, what do we do?

How do you copy striped raw LVs?

How do we convert the striped raw LVs to un-striped raw LVs? I'm not even sure how to copy raw volumes. I don't work with them much...

[Pete Randall]

Stuart,

How are these LV's striped? It sounds like it must be at the hardware level. If that's the case then the question of LVM striping doesn't even come into play. Just mirror from old EMC to new and let the hardware handle the striping.


Pete

[Ashwani Kashyap]

You cannot use LVM mirroring with LVM BLOCK striping.
BLOCK striping means that you use the -i and -I options with lvcreate .

However, you can use LVM extent striping with LVM mirror.
Extent striping means that you used the -D option with lvcreate . Again mirroring will only succed if you have enough PE's in the VG's to accomodate the mirrors .

Migrating RAW volumes are tricky , because you don't know the contents . Only the application knows how to rad the contents .

The best way to move them to the EMC is either by a backup/restore software that understabs the raw data or by some other means in the application itself .

THe other method that I have used in the past is to used dd to move the raw contents from old logical volume to the new one . But it requires down time and also the application config files needstto be changed to point from the older raw logical volumes to the new eaw logical volumes (/dev/vgXX/rlvxx

[Sundar_7]

From your previous post, I understand your LV is striped using LVM not at the hardware level ? - is that right ?

If yes, then you can use dd to achieve the results for both the striped and raw volumes.

1) Make the NEW(DMX) disks visible to the host
2) Add the PVs to the VG
3) execute dd and copy from the old disk to the new disk

# dd if=/dev/rdsk/c6t5d0 of=/dev/rdsk/c12t5d0 bs=1024k

Execute the dd command for all the physical volumes.
4) You can execute dd even for copying raw logical volumes (I believe so :-)).
5) Once dd is complete, deactivate the volume group
6) Remove access to the OLD disks for the system. i.e disable the host from seeing the OLD(3930) disks.
7) activate the volume group (You might have to activate the VG disabling the quorum)
8) execute vgreduce -f option. This will remove all the missing OLD disks from the vg configuration.
9) Now your VG is up with the disks from the DMX. 3930 copies are stil intact.

Sounds good ?

[Stuart Abramson_2]

They are "LVM-striped" LVs.

..lvcreate -i 8 -I 64 -n lvol${LV} vgXX
..lvextend -L 2000 /dev/vgXX/lvol${LV} pv01 pv02 ... pv08

They are LVM "byte-striped" LVs. And, they're raw volumes - not mounted.

[Stuart Abramson_2]

Thanks for all your responses.

However, let me say again:

The old VGs/LVs are already created so I can't recreate them.

I want to convert raw striped volumes to raw un-striped volumes. I mean LVM striping.

dd'ing a disk that is a striped volume will result in another disk that is also striped.

I know that I will have to shut down and modify the application.

How does this sound:

create new LVs on unstriped disks.

..dd i=/dev/vgold/LV1 o=dd/vgnew/LV1N

where vgold is striped and vgnew is not striped?

Will something like that work?

How do you copy raw LVs from one raw LV to another raw LV?

[Sanjay_6]

Hi,

LVM doesn't support striping & mirroring. Can you try SRDF between the two EMC's and keep the data in sync that way, instead of doing a software level mirroring.

Hope this helps.

Regds

[Dave Wherry]

SRDF is a good suggestion.
EMC has always been good about offering data migration services. I'm surprised they haven't already approached you about it. They will, for a fee of course, temporarily install SRDF and help you move the data.

[Geoff Wild]

Why not use vxdump/vxrestore?

Create new vg's the way you want them, mount them under a temp mount point, say /zmnt, then:

vxdump -0 -f - -s 1000000 -b 16 /oracle | (cd /zmnt/oracle ; vxrestore rf -)

Rgds...Geoff

[George Petrides_1]

Install Data Protector, it comes with 60 days demo license, do a backup of raw volume (striped) and recover it to the un-striped...
George