Not getting close to rated speeds on LTO4 drives

[darkoverlord2279]

I have a SAS connected Dell TL2000 with a LTO4 tape head. The rated speed for LTO4 is supposed to be 130MB/sec, but the fastest speed I got is 83 MB/sec(which is almost as fast as a LTO3 drive). I tried to test backups by selecting files from a local drive and not through the network. i'm using the default block size and buffer size, and also tried increasing those values, but it didnt change the overall average speed.

Anyone else have a problem of not getting the rated speed for a LTO4 drive? I've called up Dell and they said the device was configured correctly and they arent sure why the speed is that slow.

 

[vdinenna]

I had a simular problem while using Backup Exec. If I used a copy of a job, the backup would run slow. Creating a new job for some reason allowed the tape to run faster. It could have been a software database thing, I don't know for sure.

We upgraded backup software over old versions for several generations. I don't think this good either. A clean install is a good thing.

With a copy of a job we got 400+ meg/min backups. Backing up from a new job got us 900+ meg/min. This was with LTO1 hardware. Verifing was even faster.

Hope this helps,

Vince

 

[jimbo456]

Just some thoughts off the cuff. We had a situation where one of our Windows clients took forever to bu. Come to find out it was an index issue. 65,000 directories with one file in each directory, it took forever to build the index. You didn't mention if you were using windows or linux. Try doing some testing on a different os. You might find that the scsi behaves better with the different os. Take a look at the scsi Firmware. Upgrade the firmware??. Look at tuning the raid, recording disk access, paging ect. Look at changing the scsi cable. It might be holding down speeds (Doubtfull) Find some software that records scsi statistics and check with the manufacturer for benchmarks.

Just some thoughts.

 

[LWComputingMVP]

Backup speeds depend on a variety of factors. Disk usage at the time of backup, the size of the files, the fragmentation of the files. The driver used for the SCSI card that controls the backup drive (I once had HORRIBLE performance with a SDLT drive (30 MB/Min) and it turned out it was a driver issue. Fixed the driver issue and the performance jumped to over 300 MB/Min.