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Mixing LTO in multi-unit library configuration

Fernando Boza
Regular Advisor

Mixing LTO in multi-unit library configuration

Hi

I have 2 MSL6060 in multi-unit library configuration. The first MSL6060 have 2 LTO3 and the second MSL6060 have 2 LTO4.

The Problem:
I have 2 servers with HP-UX v1 ... from both servers the troughput to LTO4 is low... similar to LTO3.

I execute tar tests... and the result is similar for both LTO

What happend?
3 REPLIES
Rob Leadbeater
Honored Contributor

Re: Mixing LTO in multi-unit library configuration

Hi,

How do you have the library cabled ?
Fibre or SCSI ?

The MSL6060 has some limitations with regards to speed.

See these two advisories:

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=c00598538〈=en&cc=us&taskId=101&prodSeriesId=316040&prodTypeId=12169

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=c01122518〈=en&cc=us&taskId=101&prodSeriesId=316040&prodTypeId=12169

Hope this helps,

Regards,

Rob
Fernando Boza
Regular Advisor

Re: Mixing LTO in multi-unit library configuration

The conectios is FC with NSR
TTr
Honored Contributor

Re: Mixing LTO in multi-unit library configuration

The LTO4 drives are very fast. Even if you have the connection bandwidth, you must pump enough data to the LTO4 drives to keep them streaming otherwise they will give you poor performance, same or worse than the LTO3 drives.
The LTO4 drive needs to have data delivered to it at a rate of 35MB/s minimum. If you can not deliver that much data, it would stop and start endlessly (shoeshine effect) and give you poor perfromance and eventually it will get damaged.

> I execute tar tests... and the result is similar for both LTO

This test is not the right test for tape drives. The tar command can not deliver enough data to take advantage of the LTO4 drive speeds. It is a single stream i/o.

What do you use the run your backups? If you have an enterprise backup system such as NetBackup or Data Protector, they can deliver data to the tape library in multiple streams from many different sources and keep the LTO4 drive busy to take advantage of its performance.
You also need a dedicated backup server that is also very fast and can deliver data to the LTO4 drives in fast rates. That means the backup server must be able to collect the backup data ata the same fast rate.