Newbie: Hotswap disks

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Newbie: Hotswap disks

channel_zero
Hi,

I'm a newbie that has mhvtl setup to emulate an HP changer with ultrium drive per a number of examples.  Nothing special going on with the config.  The box is an old tower with a SATA hot swap tray. The bios supports hot swap.  I'm using tgt to export the emulated tape changer.  To get things working, I mount the hotswap disk to /opt. Hosts see it and everything works great.  

I have two further goals:
1. Rotate the hotswap disk, taking them offsite for backup/DR.
1a. Furthermore, each disk should have a unique set of simulated tape.  

Is that possible with mhvtl now? (09-2013)

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Re: Newbie: Hotswap disks

channel_zero
I poked around at the file structure and moved the hotswap disk to another mount point, /mnt/tape.  Then I made symbolic links from /opt/mhvtl/90/tapexxxyyzzzz  The daemon runs fine like this, but, please let me know if that's not a good way to solve the problem.

The question of how to replace the hotswap drives and populate each drive with its own set of virtual tapes is still open.
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Re: Newbie: Hotswap disks

Mark Harvey
Administrator
OK - first off, a sanity check..

Why are you trying this ?
Surely the backup application can handle disk better than using software (mhVTL) to convert perfectly good disk (random access) into sequential access..

Now that is out of the way, onto ideas / hacks to get this to work :)

If you linked /etc/mhvtl/library_contents.xx -> /mnt/tape/library_contents.xx
When you swap your disk /mnt/tape, you "pkill -HUP vtllibrary" which will re-read the library_contents.xx
I would strongly recommend keeping the number of drives the same across each instance - but you can change the number of storage slots, mail slots (if you like).

As long as no tapes are mounted at the time of the disk swap - all will be good..

To be sure, before you swap out the disk run the following checks
 - mtx -f /dev/sgXX status | grep "Data Transfer Element" | grep -v Empty | wc -l
(Should return 0)

Take the library in an offline state (which will prevent anything from moving media into a drive)
 - vtlcmd <index> offline

Swap disk
 - vtlcmd <index> online
 - pkill -HUP vtllibrary

Re-inventory the robot using your application software..

Please post your experience - good or bad and any ideas you think may help.
Regards from Australia
Mark Harvey
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Re: Newbie: Hotswap disks

channel_zero
Thanks for the tip on how to do the swap.  I'll post results when I have them later this month.

The simplified reason we're doing this is to keep a legacy system going with minimal changes.  This looks like it will work well.