Amanda: Backing Up Volumes Larger then 1 Tape

sbabcock23 · 09-29-2010, 09:57 PM

Hi,

I am new to Amanda. I can backup anything that is smaller then a single LTO4 tape, however I have one DLE where the amount of information I want to backup is 950GB (which happens to be on the backup server) but the tape is only 800GB. How can I get this to span multiple tapes for a single DLE?

I have set the tape_splitsize to 5GB for right now, but it is taking forever to backup the volume. Because the volume is larger then the holding disk, Amanda resorts to the fallback_splitsize which I have set to 1GB. My understanding is that this basically stores 1GB of data in memory and then writes it to tape?

Since I have a holding disk of 200GB, is there a way I can write 80GB of data to tape instead of 1GB chunks at a time?

What is the ideal way to backup large amounts of data by spanning multiple tapes and writing to the tape as quickly as possible?

Thanks for your help,
Steve

choogendyk · 10-01-2010, 06:36 AM

Is it working (across more than one tape), but just slow? Or is it not working across more than one tape?

Are your drive that you are backing up and your holding disk on separate spindles? Is the tape drive on a separate interface? What are the specs on your computer, and what else is it doing? There are a lot of factors that go into performance for tape backup, and getting throughput on LTO4 requires that all the other components be able to keep up. How slow is slow? Can you tell how many MB/s you are getting? 950GB should take a few hours in any case.

To eliminate variables, try just tar or dd from the backup drive to the tape to see if your hardware is up to the task. Are you using hardware compression? That 950GB should actually fit on one tape unless it is just plain uncompressable. Using software compression makes planning easier for Amanda (because it knows the results of the compression and can be fairly accurate about what will fit on the tape), but then you need a fast CPU to keep the throughput high enough for the LTO4.

Anyway, not much point in trying to tune amanda.conf parameters until those other questions are answered. I've seen people happily driving TB's of data to LTO4 with Amanda, but with well tuned servers that are not bottlenecking at other points.