Ultrium2 performance is slow in N4000 machine

[vijay_56]

Hi all,

I have connected Ultrium2 external drive to a N4000 server through a Ultra2 scsi adapter. The server firmware is update and latest patches are installed. But the tar backup is taking place at the rate of 1GB in 10 minutes, which is a ultimate slow. is this due to usage of ultra2 card.

With Regards,
Vijay

[Kurt Beyers. · Accepted solution]

Vijay,

An Ultrium2 can write up to 100 GB/hour. The Ultra2 SCSI has a thorugput of 150 GB/hour, so it isn't the bottleneck.

To evaluate the speed of the Ultrium2, take a backup (eg with fbackup) of a few large files (large is larger than 1 GB). You'll should have a good throughput now.

I rather think the low throughput of the tar is because a lot of small files are being backed up, then the troughput is always smaller.

best regards,

Kurt

[Trond Haugen]

when testing for performance it is always good to test as few things as posible at a time.
With your setup you are testing disk, tapedrive and backup utility at the same time.
My advice is to use time and dd to test one thing at a time. You may need to start with creating a "bitbucket" to read from:
mknod /dev/bitbucket c 3 3

Creat a 1Gb file on disk:
time dd if=/dev/bitbucket bs=1024k count=1024 of=/mnt/bigfile

Send the same amount of data to the tapedrive:
time dd if=/dev/bitbucket bs=1024k count=1024 of=/dev/rmt/0m

Check how long it takes to read the file:
time dd if=/mnt/bigfile of=/dev/null

Remember to umount and mount the filesystem with the big file each time you have read it to clear your cache.
Send the file to tape:
time dd if=/mnt/bigfile of=/dev/rmt/0m

If nether of these take as long as your backup I would say your problem is the backup utility. OR the fact that the backup have to search and backup a lot of files. You could also try backing up just that one big file.

Regards,
Trond

[Sยภเl Kย๓คг]

As Kurt said you may be backingup smaller files.Try backing up some files which is more than 1GB in size.Can just give brief history.Was the Drive giving good performance earlier.When is this problem started and what is last change made to the system just before the problem started.

regards
SK

[Joe Short]

To get the most out of LTO, you need to flood it with data. If the data stream is slow or unsteady, the drive will be stopping and starting as it waits for data. Generally, if you are connecting an LTO to a SCSI HBA, you want a single LTO to be the only device on the SCSI bus. Otherwise, you may find contention for bandwidth on the bus.
Your backup will only be as fast as the slowest part of the whole process, so if you are backing data across a 10MB network, than that is as fast as you can expect your backup to be. You did not say if the LTO was directly connected to the server you are backing up from, or remotely connected.

Also, you can download library and tape tools for HP-UX 11.x from this URL.

http://h20000.www2.hp.com/bizsupport/TechSupport/DriverDownload.jsp?pnameOID=316112&locale=en_US&taskId=135&prodSeriesId=316104&prodTypeId=12169&swEnvOID=7

With this tool, you can execute a performance analysis of the drive and eliminate any other components that may be slowing things down.

[Jeff Schussele]

Hi Vijay,

I agree 100% with Joe.
This tape drive should be the *only* device on the bus save the HBA. If you're feeding it with drives on the same bus, it will never keep streaming. And that's the key. Anytime it has to stop & reposition performance will just go to heck. Plus it will cause premature wear on the tape drive head - dratsically shortening it's lifetime.

My 2 cents,
Jeff

[Ted Buis]

You could time your tar output to /dev/null and take the tape out of the equation. Trond showed how to test the tape's ability, but it really doesn't test your files and filesystem's ability to generate a stream of data.

[Mohanasundaram_1]

Hi Vijay,

In addition to what was told in this thread already, please note the native backup utilities are not expected to give the maximum performance.

You have to use a backup software like dataprotector to get the maximum performance out of the backup device.

With regards,
Mohan.