Legato: Backup Speed Problem.

[Ashwin_4]

Hi Masters,
I'm trying to take system backup (SAN) using DLT Tape Library. nsrwatch shows that backup is taken at11 Mb/s.
02:/dev/rmt1.1(J) LTO Ultrium A00017L1 2:writing at 11 MB/s, ......

Can I speed up the backup process, if yes HOW?
Following is the command i'm using to take backup,

save -s ctyhnm01.mtnlcty.com -b W1TRSYS1 -c west1tr -I $BAK_HOME/if_full -N FULL_W1TR

Thanks.

[Robert-Jan Goossens]

Hi Ashwin,

Looks like you are using LTO drives, can you post what kind of network speeds you are using ?

Best regards,
Robert-Jan

[Leif Halvarsson_2]

Hi,

You talk about DLT Tape Library but, the device seems to be a Ultrium ?

Speeding up backup processes is very much identifying the bottleneck(s). In most cases, the problem is with the disk/filesystem. You need a very fast disk system to stream a Ultrium 2 device.

Also the type of data you backup can have big impact on backup speed. Millions of small files will slow down performance or, compression ratio for the data (high ratio increases throughput).

[Ashwin_4]

Hi,
You r right, its a LTO ultrium.

[Florian Heigl (new acc)]

Sometimes NetWorker is unable to properly set it's usual 32k blocksize - skim over /nsr/daemon.log for such messages, wrong block size (or density!) settings are prime reasons for unexpectedly low tape performance.

Also, as Robert already asked, the 11MB/s sound very much like a bottleneck (FastEthernet, that is) on the way.

Do You get higher performance when running i.e. save -s ctyhnm01.mtnlcty.com -c ctyhnm01.mtnlcty.com [...] ?
In that case, definitely suspect a network bottleneck.
In rare cases, the policy settings could also pose a problem, if the client in question is using 'unix with compress' and is too slow compressing.

Also, of course the data being backuped and parallelism setttings are questionable.

To do first things first, please just umount (+disable for service) the tape, insert a scratch tape, and see what throughput You see when issuing a
timex dd if=/dev/zero of=/dev/rmt/0mn bs=1024k obs=64k count=1024

If this is still below something like 40MB/s, You should gather some manuals and look after the density settings, and look for fibrechannel error stats.

[morganelan]

If You want to speed up the backup process, you must tuning your Legato Networker Server.Change some kernel parameter such as nfile,maxfiles,
maxfiles_lim and nproc.

[Bill Hassell]

Is this a network backup (ie, not a local disk to a local tape)? If so, you cannot supply data fast enough for the LTO drive to work properly if your network card is 100Mbits or less. 100Mbits translates to about 10Mbytes/sec fully saturated, but you really won't get much more than 5-8Mbytes/sec on a shared LAN. Now Networker may be compressing the data before sending it on the LAN which gives you about 11Mbytes/sec, less than 1/4 of what is required.

Notice that I said required? Modern tape drives are extremely slow when the data rate is not fast enough to keep up with the drive. The drive has to stop, backup and take a running start to resync and start recording once the data catches up with the tape. You'll need a dedicated 1000Mbit link to keep the tape running at full speed.