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Slow Throughput rate of LTO4 drive in a HP StorageWorks 4048 Tape Library

nico- asked
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Last Modified: 2013-12-01
I'm just consolidating 7 x BackupExec 9.1 into one  BackupExec 11D server, which runs on Window's 2003.  The server is attached via a fibre switch to a HP StorageWorks MSL 4048 with 2 x LTO4 drives.  One of the drives is faulty and we're awaiting a replacement drive.

I have been able to play around with the other tape drive in order to gage throughput rates that will hopefully tell me if 2TB can be backed up overnight.  The working tape drive is currently running at 160mb per min, yet when I used the latest version of the L&TT to run a drive performance test and the working drive is running at 98MB a second.  Having performed a health check on the working drive, the following message appears under the drive analysis section.

"There are indications that the drive is experiencing a high polling rate on the scsi interface.  This could be due to RSM or it could be due to another host.  High Polling rates ca interrupt the normal operation of the drive and significantly reduce performance"

The Removable Storage service isn't running (if that is the relevant service?).

HP have advised Feb 6th as the day when the replacement LTO4 Tape Drive will be available (shortage of devices apprantly), so i just wanted to know if it is the faulty tape that is likely to be causing the tape drive to backup at 160mb per min rather than 6gb per min.

The latest firmware and windows updates have been installed.

Best Regards
Watch Question

The problem drive in most cases will not cause a problem especially in a SAN environment.
Yes RSM is Removable Storage Service and yes it should be disabled.
Only the backup server should be able to see the tape library, zoning should be setup so no other server or NAS filer can see the tape library.
For best throughput each LTO4 drive should have its own HBA bus.
Multiplexing should be used since it is unlikely a single backup source can fully utilize an LTO4.
Go for an update to the tape drive driver, I'm not sure which is better the BE or HP one.
HP Management Agents can also cause problems.
   Control Panel > HP Management Agents > make sure SCSI Information is in the Right Window so it will not be collected.



Thank you for your response.  Most Kind.
I am only intermediary level, so will ask you for further information/detail if that is okay?

RSM is disabled.  The latest tape drivers (HP) have been installed.  There is no SAN or NAS setup here.

I don't understand what is meant by zoning?  I've heard of partitioning in BE but not zoning.
I'm not sure how i can effect LTO4 drives onto its own HBA bus.  Could you give more detail here please?  I know what is meant by multiplexing, but do not understand how i can implement that in this context.
There is no HP Management Agents Icon in the control panel.

any help appreciated.

Thanks in advance
Your entry says:
"The server is attached via a fibre switch to a HP StorageWorks MSL 4048 with 2 x LTO4 drives. "
If you have a Fibre switch you have a SAN and whoever administers the switch is the one to configure the zoning.

The Fibre channel model of the library comes with Fibre direct tape drives so it can support two Fibre connections. Get with whoever administers your library to verify this.

Multiplexing is setup within BE when configuring the jobs.



Thanks for the information on Zoning.

You never replied with the information on LTO4 drives and separate HBA buses.   Would you mind explaining how i would effect this please ?

Regards Multiplexing, I've never found a setting and this article seems to disagree with you


as does this


They could of course be wrong and you could be right.  If so, could you explain in more depth than "multiplexing is setup within BE when configuring jobs" as i am an intermediate user of backup exec as stated above.  With fear of sounding confrontational, which is not the case, simply stating something works or doesn't work isn't generally enough when trying to explain a new concept to someone surely ?

Iamthecreator OMIT/EE Solution Guide
Also the HP Lib and Tape Tools is not a good way to check the throughput as it simply generates a string on data and writes it to tape which is not what happens when you run a backup as the backup might have to transfer data over the network
Also different resources will have different trhoughput depending on a lot of factors

Please refer to the following articles

Reasons why the data throughput rate can be slower than the theoretical maximum when backing up to tape media

Improving and troubleshooting Backup Exec performance

sorry about the mis info on BE's support of multiplexing, I'm an ARCserve user and have limited familiarity with BE. I just figured that since in most cases multiplexing is the only way to achieve maximum throughput with LTO3 and especially LTO4 drives that BE would support it.

For details on how to setup the hardware either Get with whoever administers your library to verify this. or check the manual for the drive.

Regardless it will not drive throughput down to only 160mp/m. Oh an forget about 6gb per min. because that is not realistic.

By the way I'm guessing that the LTO4 are already running on the BE 11 system because earlier versions are not certified compatible with LTO4.

What type of data is being backed up and where does it reside?
Is the throughput 160mb/m for each volume being backed up or does it vary from volume to volume?
If you are backing up compressed data and data over the network as apposed to SAN attached data 160mb/m may be the best you can do.
Iamthecreator OMIT/EE Solution Guide

Also are we  using the latest device drivers for the TAPE drive if not please download and install the following package

Symantec Backup Exec (tm) 11d (11.0.7170) - Device Driver Installer (20071215) - Includes Tape Driver Release (34) and Robotic Library Release (81) (x86-32 bit)
Document ID: 294731



No problem at all with the multiplexing.

Current backup is BE 9 to standalone drives (LTO1-3's).  Some of the BE9 servers are backing up remote systems using remote agents.  The thing is, the throughput rates on these older servers, older drives, with older media, over the same network, is between 650mb - 800mb per min !  Therefore it rather points to a bottleneck/settings issue with BE11D, the fibre channel switch and the robot.  Which is really the question of where best to look at ?

In fact, even running a backup from the local hard drive results in rates of 160MB per min.

Compression is set to hardware compression in BE.  

That was my next question, local backup.

Get with the SAN admin. Have them verify the zoning so only the backup server sees the tape library. Next have him enable logging on the switch and then run a backup. Check the switch's log to see if there is a high error count and if it is on the server or library side. This can at least narrow it down to something along the line of a problem between the server and the switch or the library and the switch.



Thank you all.  Very useful knowledge.

I'm waiting on HP to deliver the replacement HP LTO4 drive on 6th Feb (3-4 week lead time!).

In the meantime, I'll check the fibre switch to see if Zoning is configured and also check the throughput rate on the switch from a local server backup and from a remote server (via remote agent).

The latest symantec patch (7170) is installed.  The latest HP Tape Drivers ( are also installed by updating the driver using the windows update option).

I'll leave the question open.


I'm going to carry on leaving the call open as the LTO4 drive has not arrived yet with the engineer who originally configured the san switch, so there's nothing further i can try.


No final answer as they've run out of budget and i'm therefore off the project before i could see if the solutions worked!


ahhh ..

The HP Engineer has finally arrived with the LTO4 replacement drive, 12 working days later on a 4hour contract.  Nice.

It's completely fixed the problem with speed.  Now running between 1.3GB per min and 3.5 GB per min.

Whoever mentioned SCSI chatter, that's what it was


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