Re: [Veritas-bu] NDMP

server_param server_x -f PAX -l will show you the settings for PAX.

readWriteBlockSizeInKB is the parameter you want to change to 256kb. This will require a datamover reboot, but you could always fail-over and fail-back the datamover in question to minimize any downtime. CIFS clients will probably need to reconnect, NFS should recover.

There is also a bufsz parameter you can change under the NDMP facility as well, but this will not affect the block size written to tape like readWriteBlockSizeInKB.

You also may need to touch SIZE_DATA_BUFFERS_NDMP, depending on your version of NBU.

-- nick

You need to get from EMC PowerLink the latest version of their document "
Configuring NDMP Backups on Celerra". I think a number of the suggestions
that I've seen only apply to 'remote NDMP' where the tapes are on a
'normal' media server with the ndmpmoveragent running, and the data comes
from the disk mover on the Celerra to the tape move on the media server.

If you have tapes connected directly to the Celerra, you must follow the
EMC manuals, and you have quite a bit of control. I'm not sure you can
increase the buffer size, it may depend on your DART version. We've got
rid of our Celerras, so the information I have is quite old.

However there is a PAX parameter:

name = readWriteBlockSizeInKB
facility_name = PAX
default_value = 64
current_value = 64
configured_value =
user_action = reboot DataMover
change_effective = reboot DataMover
range = (64,256)
description = Maximum allowed PAX buffer size for NDMP read/write in
kilobytes

I'm not absolutely certain that this is the tape block size, as it is
described as "Sets the maximum allowed PAX (portable archive interchange)
buffer size in KB for NDMP read/write operations." It definitely will
change the buffer size between the various threads handling NDMP on the
Celerras. However you can clearly use the server_pax -stats command to
see what it is using as in one of the examples it shows NASW (the thread
the write to tape):

$ server_pax <movername> -stats -verbose

.
---- NASW STATS ----
nasw00 BACKUP (in progress)
Session Total Time: 00:00:08 (h:min:sec)
Session Idle Time: 00:00:00 (h:min:sec)
KB Tranferred: 98406 Block Size: 64512 (63 KB)
Average Transfer Rate: 12 MB/Sec 42 GB/Hour
Average Burst Transfer: 12 MB/Sec 42 GB/Hour

See the 'block size'.

There are many tuning parameters, and the manual has whole flowcharts for
tuning backups & restores. But, you do need to be able to reboot the data
mover....so you need that failover window.

William D L Brown

> > On that same subject, anyone have any suggestions for tuning an
> older EMC Celerra environment? I would like to get my tape buffers
> up to 256K but can't make heads or tails of the configuration
> parameters. I don't have much chance to play with the parameter
> since the documentation indicates a reboot of the data movers is
> required. These are 24x7 devices.

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