Alternate Boot Disk

[Craig Rants]

I need to create a bootable disk of server1 on server2.

Assumptions:
1. server1 and server2 are the same architecture and have the same components
2. Only vg00 needs to be replicated
3. server2 will be functional as a unique server until required to replace server1 (lets say that server2 is a test server which is used a lot, but is expendable when needed)

The requirements are as follows:

1. It needs to be ready at a moments notice, i.e. if server1 goes down, server2 can be rebooted, the boot disk can be changed to something other than server1's pri and alt boot disks, server2 comes up and looks acts as server1 with nobody knowing the difference (except for apps who care about the arp table but that is not a big deal right now)
2. server2 can not go down to complete this altroot process.
3. The altroot process will happen on a weekly basis

I have been thinking about some nfs type of connection to complete this, but this is just theory right now.

Any ideas are welcome.

Thanks,
Craig

[harry d brown jr]

You could use ignite to build the second server, but it wouldn't keep it in sync.

Your other choices are to get a hass rack, 12H, VA7100, VA7400, or EMC Symmetrix type of disks - something that can have multiple hosts physically attached to them.

When server A (the main one) dies, then boot the second one (server B) using the boot/root disk server A was using. It would be assumed that both servers are identical though!

live free or die
harry

[harry d brown jr]

Another choice, although expensive (that's depends upon the application requirements) is MC Service Guard.

live free or die
harry

[Sridhar Bhaskarla]

Hi Craig,

We were doing a similar excersize in my past company where we used to import the root volume group from the EMC disks onto other systems. Both the disks will be in sync all the time on EMC. If server1 goes down, we split the mirrors and boot server2 through the mirror.

-Sri

[Craig Rants]

Ok, more assumptions,

No hardware can be purchased

No ignite servers can be used (because of the location on the network, the two boxes are isolated)

See why I am looking for ideas.

Thanks,
Craig

[Craig Rants]

We've dome mirror splits on our EMC as well, unfortunately, these two boxes are on their own and can't share an Autoraid or EMC.

Thanks

[harry d brown jr]

RSYNC

http://hpux.cs.utah.edu/hppd/hpux/Networking/Admin/rsync-2.5.1/


live free or die
harry

[Christopher McCray_1]

For the vg00 part, definately Harry's suggestion is good with the ignite tape. As for it's ability to "take over" for server1, I would go with MC/ServiceGuard. I know this is a canned answer and a costly one at that, but your server two could be the failover node in a two node cluster for your production applications and all your test-related apps could be outside the cluster, so It wouldn't be part of the failover scenario and possibly burden your primary server by having the possibility to fail over to server one. Just my two cents because I like MCSG so much.

Good luck.

Chris

[Helen French]

Craig,

Interesting .. Seems like it's almost same like the old 'Switch Over Unix' software which was running on HP-UX 9.X and no more supported now. Just some few things from that point:

1) Use a common diskstation for both server1 and server2. The alternate root disk should remain in this diskstation. This diskstation should be accessible to server2 through an alternate cable. Also all applications should remain in the common diskstation.

2) The alternate boot disk should be like a mirror copy of the server1's root disk. This mirroring can be done on your convenience.

3) Now, if server1 goes down, restart the server2 and change the boot path to the alternate root disk, which remains in the diskstation. This will boot the server with all applications.

4) Here, the server2 normal jobs/applications will be kept pending during the down time of the server1.

5) Once everything is set back on server1, you can shutdown server2 and mirror back the root disk to the original one. This will be easy if you keep both mirror disks in the common diskstation.

However, I have tried this set up long ago and not sure whether this helps you. Using an HA software will be the best solution.

HTH,
Shiju

[Craig Rants]

Nancy, thanks for the script, we have something just like this to create an altenate boot disk (besides the mirror copy). I would like not to have to move the disk from one box to another, that was why I was thinking trying to do this through nfs somehow.

Craig

[Patrick Wallek]

You don't have to use an Ignite SERVER to do this. IF these machines have tape drives, then you can install Ignite/US (you can get it off the application CDs or from http://software.hp.com/products/IUX ) and then use the make_tape_recovery command to create a bootable tape of your entire VG00 from server1. Then you put that tape into server2, boot from it, change your IP address and you are ready to go.

The command I use, if you are interested is:

/opt/ignite/bin/make_tape_recovery -a /dev/rmt/0mn -I -v -x inc_entire=vg00

[Darrell Allen]

Hi Craig,

Blue skying so I don't know if this will work but you asked for ideas...

On server2, do the pvcreate -B, mkboot, lvcreates, etc that you would do for a boot disk. Basically, set up the disk without data.

Then to get the data there, I see 2 possibilities:

server1# dd if=/dev/vg00/lvol3 bs=64k | remsh server2 dd of=/dev/vg##/lvol3 bs=64k

-or-

server1# cd /
server1# find . -depth -xdev -print | cpio -oxcB | remsh
server2 (cd /new;cpio -idumB)

Again, it's an idea, not a tested method.

Darrell

[Craig Rants]

Thanks for all the input. I found a smart enclosure, so I think that I am going to have them share the smart enclosure and have server1 create the altboot disk, then when server1 goes down have server2 boot from it. I'll keep Patrick's idea as a secondary plan.

Craig

[Darrell Allen]

Hi again,

I didn't test the dd copy but I did try the cpio. It didn't work as I first posted.

It will copy a directory structure if changed like this:

server1# cd /dir
server1# find . -print | cpio -oxcB | remsh server2 "cd /dir;cpio -imdcB"

I created /dir on the destination system before running the command.

Darrell