Slow Write Speed LTO 5 Backup Exec 2010 R2

I have been struggling with an issue involving the write speed of my new LTO 5 HH SAS drives with Backup Exec 2010 R2. I recently replaced a dead LTO 3 library with a new Tandberg T24 LTO 5  library. I moved the backup jobs to a fresh install of server 2003 R2 Standard, and a new install of Backup Exec 2010 R2 Sp1.  The problem i have had is the write speed for the new drives is much slower than anticipated, previously on the LTO3 library backup jobs ran at about 1,300 MB/min and with the current LTO 5 I average 850 MB/min. What parts of the puzzle am i missing to get the potential write speed out of these drives.  Symantec support has been less than helpful thus far with over one hour hold times, and a atrocious website. Please help

Relevant  Info
Using symantec drivers for the Tape Drives.
Default windows driver for library (as recommended by symantec support)
Current Firmware on both Library and drives
Backup exec patched to current version
OS: Window Server 2003 R2 Standard x86
Tanner CroweAsked:
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andyalderSaggar maker's framemakerCommented:
The Tandberg LTO3 HH supports speeds of 20-60 MB/s - 1200 - 3600 MB/min so by the looks of it you were able to read from your Exchange server just fast enough to keep up with the minimum speed of the tape drive.

The LTO5 HH though is faster at 47-140MB/sec, and since you can't read from your Exchange server that fast it has to keep stop-rewind-write (shoeshining) which slows the job down further and also wears the tape head out. THis is a common problem with fast tape drives, they are often too fast for the data source.
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Tanner CroweAuthor Commented:
The issue is not with backing up a particular server, this issue is the over all write speed of a entire backup job. The previous library was a dell LTO 3 Powervault 132T SCSI connected. The current Library is a Tandberg T24 with LTO 5 HH SAS drives. My write speeds on the new library are very slow, I have monitored the servers performance during backups and i do not see a bottle neck in network or hardware performance.

I also have issues with the Tandberg Library not being able to complete a full inventory in Backup Exec
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andyalderSaggar maker's framemakerCommented:
What do Tandberg support say? Have they got you to run a diagnostic on it independent of Backup Exec?
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tsmgeekCommented:
all the LTO5 drives look very similar, ive been readin up about them and they have variable write speed (well the HP ones seem too) to stop the 'shoeshining' effect that andyalder was talking about, check with tandberg that their unit supports variable write speed as if not then thats possably the issue
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andyalderSaggar maker's framemakerCommented:
The 47-140MB/sec I posted above is the variable speed for the Tandberg.
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Gerald ConnollyCommented:
The main LTO drives in the marketplace are either from HP or IBM (or were last time i looked) Both IBM and HP have implemented strategies to mitigate against shoe-shining but ultimately there is a minimum speed below which the drive slips into shoe-shining mode and the performance then drops off a cliff.

I haven't seen the exact detail of how it is implemented in the LTO5 generation but in previous generations IBM implemented a stepped speed scheme, whereas HP had a continuous variable speed implementation.

I agree with Andy, your disks just aren't delivering enough speed to reach the minimum speed for your new LTO-5 drives. Its very common for people to upgrade from slower tape drives to the latest whizz-bang (faster) version and get slower backup speeds.

Why does it happen?
Well, LTO is a streaming tape drive and runs continously until the data in its cache runs out, at this point it needs to slow down to a stop, reverse back past the point it ran out of data, back far enough so it can get back up to speed by the time it gets to the "out of data" point and continues writing from there. If your backup application cannot fill the drive cache quick enough the process will be repeated over and over again hence trashing the overall write speed for the device. This process is know as shoe-shining.

In the LTO2-LTO3 days Compaq recommended that the read speed off of disk was 3 times the required write speed to the tape, to make sure the tapedrive cache never emptied until the backup was complete.
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Gerald ConnollyCommented:
So obviously if this is the case then the place to start concentrating on is your disk subsystem.

What is your disk configuration? Direct Attach, SAN, iSCSI etc?
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Tanner CroweAuthor Commented:
I spoke with Tandberg support a few days ago and i have made some headway on the problem. There was an issue with my SAS adapter, the firmware and bios on the card where mismatched. After upgrading the card, i have been able to inventory successfully and i have run Diagnostics independent of backup exec. Using a diagnostic utility i was able to to a I/O test on the drives. My average write speed was about 4100MB/min and 8000MB/min. However i still suffer from reduced write speed in backup exec. The disk configuration is direct attach for the backups. I still get a very low job rate in backup exec about 850MB/min that is about on par with a previous LTO3 drive I used for backup. What possible steps can i take to improve the performance of the backup jobs? Would it make sense to add a multiple network connections and possibly team the NICs?
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Gerald ConnollyCommented:
So 4100MB/min is 68MB/s (what was the 8000MB/min?) so thats above the minimum according to andy.

What does your config look like as you mention directly attached disks and network devices.

Are you doing some of the backup across a network?

It still looks like you are failing to achieve the drive minimum speed. So to improve that you need to improve your backup read speed from disk/network as you need to get the data to the drive quicker.

If your backups are coming across a network you need to somehow get the data across the network quicker, or stage the data to disk before dumping to tape.
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tsmgeekCommented:
what is the array setup you have (disks, raid level etc)
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Gerald ConnollyCommented:
The experts agree on a probably cause of the slow speed after the upgrade and offered further help. The author hasnt answered.

Please distribute points between:

ID:35298148 Author:andyalder
ID:35308767 Author:connollyg
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IT-Monkey-DaveCommented:
As connollyg mentioned, I would look into staging the data to local disk on the Backup Exec server, then write to tape from the staged data.  Doing this with ArcServe made a huge difference for us.
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