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LTO4 performance Dell LT2000 with Backup Exec 12.5

We recently purchased a new backup library a Dell Powervault TL2000 with 2 LTO4 SAS drives.  
The unit is connected to a new server running Windows 2003 R2 with SP2, Quad core with 4GB ram with a Dell Dual Sas Card.  
The library has two IBM drives in it and I have setup Backup Exec 12.5 and we are using the drivers from IBM and not Symantec.  I was using the symentc drives but read that the IBM drivers would perform better, So far I have not seen and difference.

My speeds that Im seeing for LTO4 are not that much better then what we saw with LTO2.  Im running backups through the Network and for LTO4 Im getting about 2000MB/min.
I also have two network cards connected to be ISCSI Vlan using Multipath and backing up using Off Host backups on one of our Equallogics volumes and only getting 2900MB/min.

What type of speeds should I see through the network with LTO4?
Do I need to make any tweaks to the Buffer size or block size to get better performance?  If so do I just change it in backup exec or do need to do extra steps(Format tapes, driver change etc&)?
Are they any logs I shoudl look at to see if somethng is miconfigured or causing issues.
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2 Solutions
Hedley PhillipsOwnerCommented:
The values you mention are pretty typical. LTO4 can itself attain much higher speeds and supposedly the LTO4 is capable of 432GB per hour which is 7.2GB per minute but you will find that the main bottleneck is reading from the disk. Lots of small files will slow things down considerably.

Also the typical file types found on servers these days are not highly compressible and the stated LTO4 drive specs are for 2:1 compression, basically a marketing statement.

BUE 12 onwards is able to write bigger block sizes (up to 11d the max was 64K) and LTO4 tapes really need 250K blocks.

We for example use a piece of software that creates millions of tiny files and our backups are way off the stated top speed. we spent a lot of time testing and found that we could easily treble the speeds when backing up large blocks of data.
DLIExpertsAuthor Commented:
How do I increase the block size.  Do o need to do anything with my tapes?
Hedley PhillipsOwnerCommented:
The closest tech note I can find is:


It details how to check if you need to change the block size using the bptm log first.
DLIExpertsAuthor Commented:
Implemented LTO4
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