Advanced file devices and lack of parallel read support

[ozihcs]

We've been using legatos b2d option for about a year now and while we're satisfied with its performance as a backup device, we are very disappointed with the artificial limits imposed by the media manager daemon for restore jobs.

My primary concern lies in the fact that the single session available for restores is busy while old save sets are staged to tape, and this blocks all restores including saveset cloning for hours at a time, every day.

Now, I told this to my local EMC shop and was reassured that this problem has been fixed in release 7.2 of the networker server.

However after reading the release notes I realized they were probably refering to the new functionality in the command-line restore program, which now supports direct reads from disk (ie, circumventing the nsrmmd) *but only on clients with a local mount of the adv_file device!*

Obviously this is at best a slight improvement, and in my case it's pretty much useless. Cloning & database restores is where I'm hurting the most, and both of these use the nsrmmd to retrieve data.

Anyway, since this is a Big Problem for us currently I'm hoping that someone here may have some tips on how best to live with this artificial single read limit which nsrmmd imposes on restores from adv_file devices.

 

[NWNinja]

Take a look at the tread named "Device busy when trying to restore", we have posted some possible workarounds there.
This problem is not a bug, it´s a limit in the usage of adv disk devices. Legato/EMC might work on this issue in future releases, but my guess is that it might take a while..

 

[emcaixlegato]

My workaround was to build my own cloning script, which "watches" for restores, stops cloning for the duration of the restore and then begins again when the restore has completed. Another purpose of this script was to clone everything out to tape as fast as possible, so that it can get to our offsite storage facility, but keep as many savesets as possible in the disk backup pool, in case someone has to restore something.

I asked Legato for an enhancement for this, but I suspect it will be late 2006 before they get to it, if then.