Migration Low setting

[PenBayRIS]

I was just told by one of my vendors that the lomig setting should be set to 70% to prevent it from occationally failing. I currently have it set to 0 so It migrates everything to the primary tape pool and then DRM runs and moves the files it needs to the copy pool. I am sure that 30% of my disk pool is not enough to hold the daily activity.

Basically, this sounds like a very bad idea to me, but I can't find a recommended value in the docs, so maybe I am out to lunch. Can anyone tell me why this is a good idea?

 

[djchopps0013]

You dont want it set to 0 during backups otherwise you will have migration process's running while your potentially backing up to disk pools. Its really a matter of preference, but having data being written to and read from the same disk pools at the same time will kill your disks. Default I think is 90 high and 70low. We keep ours at 95 high and 85 low, but we also control migration through an admin schedule. So usually disk pools will hit around 70% after backups run and after running ba stg commands to copy pools and some other maintenance tasks we run migration ( mig stg poolname lo=0). The whole goal would be to clear your pools to 0 before the next nights backups.

Hope this helps.

 

[heada]

The default when creating a stgpool is 90/70. For primary disk pools that are just going to be a landing zone, I use 90/1. 90% because once it hits 90% it will start a migration process and 10% of the total stgpool is enough to cover any clients still sending data while the server mounts a tape (or two) and moves data off. I use 1% as the low because I want it to empty when I start the migrate in the morning but if I use 0% it is possible that it will try to reach 0% which might not be possible (0.something % on a volume will cause migration to run forever)

-Aaron

 

[PenBayRIS]

Just to be clear, this is a maintenance script. The standard pool setting is 90/70. I don't run auto migrate typically because the script migrates the pool daily a few hours after all the backups have run.

 

[BBB]

I have no idea what the vendor was trying to say.

Setting lomig to 0 is fine if you want to drain everything off to tape ready for the next night of backups. I do it on every TSM server I have...