Slow Disk Fast Tape

[Seth_E]

Hi all,

I find that netbackup is slow when backing up to disk, yet, backup to tape (and restore from tape) is fast. However, when i log onto the media server directly , and attempt to copy files directly to the diskpool (just to test throughput between client and server) it's 110MB/sec. During backup job, it runs at 3 - 8MB / sec.

Disk STU has been set to Max Concurrent Jobs = 5, and right now, there's just this one cilent backing up to disk where it's slow. I've tested with another client and same result.

I did some reasearch and this seems to be a popular topic. I than created and modifying the below files: (no TXT extension)

NUMBER_DATA_BUFFERS_DISK = 32

SIZE_DATA_BUFFERS_DISK = 262144

The Array I'm copying too is a Raid 5 Array on a DS4700 with a 4 GB Fibre Channel Link. As stated above, copying files (via windows) to this STU is very fast, even while the backup is running .

Have any of you experienced this?

[Yogesh_Jadhav1]

Seth,

 Do you mean to say, you are trying to backup the same client via Disk & Tape and you see this difference?

 If its same client then you will have to check how the Disk Device is connected to your media servers, if its different clients then you will have to check the clients first and then move on to Disk Storage units for any issues.

[mph999 · Accepted solution]

I think you are on the right lines.

NUMBER_DATA_BUFFERS_DISK = 32

SIZE_DATA_BUFFERS_DISK = 262144

Try

NUMBER_DATA_BUFFERS_DISK = 256

SIZE_DATA_BUFFERS_DISK = 524288

Lets see if this makes any difference.

M

[Marianne]

Remember to create bptm log folder so that you can keep track of changes to buffer settings and the result in throughput after each change.

[Seth_E]

Much better.. I'm running a backup of one client (5 jobs max) to disk and it's going at 35 MB /sec.. However, this client has many files, so, this could account for the speed.

However, can I go higher with the settings you provided? Our server is 20GB of RAM and lots of CPU.

[mph999]

Sure you can try higher.

Double the number of buffers only, does that help - if not, put it back

Double the size, if no better, put it back

Then try, doubling both, again, if not better, put them back.

Martin