NDMP Direct Tape Copy woes

[ianG]

Hi folks,

Having some issues trying to get the above to work 100%.

We have a media server, writing out images to its own VTL partition (no other media servers) on a Quantum DXi, which I then wish to duplicate out to a Quantum i2k. Made a test policy, and it appears to create images that I can successfully invoke the NDMP Direct Tape Copy function on (just via manual catalog duplicate). So everything looks to be configured ok

However, there are other policies using the same storage unit, which do not use the NDMP DTC.. I just cant get my head around it.

What would stop the DTC being invoked? Is there something about these images, or the perhaps the media being used thats stopping it being invoked? I say media, as the test policy uses a different volume pool, so goes onto different tapes then the other (non-working) policies' ones - its really the only obvious difference I can see from the list of images in the catalog. Media server is the same for them all

So
When I go to duplicate a test policies image, it uses the NDMP path
When I duplicate one of the other images, it appears to ignore the NDMP path, and use the alternate FC path

Any ideas?

[ianG]

Oh dear, looks like Im not the only one thats stumped..!

We're on 6.5.5 if that helps

[ianG]

done alot of trial and error with this

comparing the two policies, chopping and changing etc, and it looks like the root of the issue is multiplexing...


Am I right in saying that you cant invoke NDMP Direct Tape Copy on multiplexed images?

[ianG]

Have opened a case with Symantec, will pass on anything of note

[David_McMullin]

with VTL, since you can create as many drives as you need, there is no need to multiplex. Unless you are trying to limit tapes used...

[ianG]

Thanks David,

yea we've been recommended to turn off multiplexing for the reasons of increasing de-dupe ratios (reduce the amount of unique NetBackup meta data created) - but that was something we were going to do down the line once we'd setting on sizings, and tape usage etc (scale back the multiplexing gradually etc)

However, if this NDMP DTC aint working at all with multiplexing, we're gonna have to seriously expedite the process - and it doesnt help us at all with our backlog of multiplexed images..

[bcblake]

Ran into this now at multiple customer sites. It could be any number of things, but here are a few to check.

Make sure destination storage unit is the i2000.

Make sure the DXi has paths to the i2000 drives (if you do it the way they suggest to set it up, you likely have SSO drives with the DXi NDMP server sharing with another media server, unless they are dedicate drives to the DXi NDMP server).

NDMP does not support multiplexing (except in NBU 7.0.1 I think where they now support remote NDMP MPX) from what I remember, even if you try to check the "preserve multiplexing" checkbox in Vault or via CLI bpduplicate.

Also check bptm logs for either:

"NDMP Direct Copy will be used", or

"NDMP Direct Copy will not be used because"

What I saw recently with a customer was the buffer settings on the media server that wrote the original image was default (65536), and the media server being used for the duplication (where the NDMP DXi physical drives were defined) was using SIZE_DATA_BUFFERS with 262144, so bptm turns off NDMP Direct Copy due to the buffer mismatch.