TS7530 - Can total drive number exeeds the default limited drive number?

[goodboy]

Hi, can you help me with some issues below:

- I create a TS3500L32 in TS7530. The default limited drive number of TS3500 is 12. Is it wrong if I create 20 tape drives? - I've aready created and it's OK. But I don't know whether this way make performance down or make some issues in the future?

- I've created 20 tape drives, and defined all in TSM Server. I make a test with only 2 nodes backing up at the same time. But the clients have to wait for a long time to "waitting for media" before transferring data. Why do nodes wait for media while I have 20 tape drives (and 100 tape cartridges)?

Thanks!

 

[chad_small]

So you have 20 drives? Doesn't make sense to me, how many drives do you have?

 

[goodboy]

Hi chad,

I also think that 20 drives/library is so much. But I think I have reason for that. It's because I use TSM to supply backup service to customers. So may be a lot of them will backup at the same time. If we have few tape drives, some customers could have to wait media for a long time before they can start. Besides, I create only some storage pools for some types of customers, so only create some tape libraries (3 tape libraries) --> many tape drives for one tape library.

I also think that 20 drives is crazy. But I do not have much experience with VTL, specially about performance. Do you can share me some experience with this issue?

Thanks a lot!

 

[peleeb]

goodboy:

20 drives is actually kind of minimal in a VTL situation, we regularly use 64 and beyond. The beauty of VTL is being able to create many virtual drives, and thus completely eliminate tape contention and increase throughput by being able to set multiple streams for processes and sessions. By setting the virtual volumes to be small (say 50 GB for regular filesystem backups), you can also vastly increase reclamation efficiency since smaller tapes reclaim much more quickly. Collocation then becomes much more attractive for restores since you can create hundres of virtual tapes (depending on your virtual volume size), and thereby considerably reduce restore times by decreasing virtual tape mounts, in addition to the fact that the "tapes" are actually disk, and therefore much faster than tape to begin with.

As to long tape mount wait times: There are a lot of factors to consider: What type of VTL you're using - is it fibre or iSCSI connected? -- what kind of HBAs you're using (2 Gb? 4 Gb?) in the host, whether the zoning's one-to-one, how much memory is available in the TSM server, etc etc.

First thing I'd look at is tape mount wait time in TSM: reduce it from the default to 2 or 3 minutes. Another thing you don't mention is whether the HBAs being used by the TSM server are using ports dedicated to tape (even in a VTL environment this has to be done, the OS sees the devices as tapes, not disk), etc etc etc. Take this post as a starting point, and best of luck on your VTL learning journey!