Slow Throughput

[Ayman Altounji]

I have a Compaq 35/70 GB DLT Product # 242520-B21, that is backing up 1.7 GB of accounting database information from one directory. It is taking 2 hours & 43 mins. to back this up! I am running on a Compaq 5500 2x Xeon 550 CPU, under SCO Open Server 5.05 with the Compaq EFS Ver 5.32a installed via Compaq Smartstart 4.60. The drive was installed via mkdev tape with the following parameters: type= cha
host apdater= 1 (system has 2
factory installed adapters)
SCSI Bus #= 0
Target ID= 6 (factory default)
Lun #= 0

The kernel was rebuilt and the system rebooted. Everything was fine.

The backup command used was:

tar cvf /dev/rStp0

The backup proceeded perfectly, except it is very very slow, and not even close to stated specs for this drive. This is totally unacceptable. This is about 140k/sec. The data is stored on Compaq Hot Pluggable 18GB 10k drives, running raid 1 (mirroring).

I would appreciate any responses as soon as possible.

Thanks,

John Stroker

[Ayman Altounji]

Similar problem with a different OS setup. We are running Novell 3.12 with all appropriate patches (including the one for the 35/70). Disk configuration is Raid 5 on a Smart Array 431 controller with four 18GB 10k drives running on a Proliant 3000 PII 300Mhz with 448MB of RAM. The Compaq 35/70 was recently put in to accommodate for larger storage. It is taking us over 10 hours to backup around 7GB (which is ~12MB/Min or 720MB/hour). The 15/30 we had in before (on a plain jane Compaq PCI SCSI adapter) was much faster than this? Our backups are successful but just waaaaay to slow. I would have to start backups aournd 9 or 10pm to be ready for users at 8am the next morning! Any suggestions???

- Will Bober (bober@derm.gov.sk.ca)

[Ayman Altounji]

try this http://support.ca.com/techbases/as61/18029.html and this http://support.ca.com/techbases/as61/10015.html
Changing block size and buffer in the Tapesvr.cfg under sys:\arcserve.6\nlm

for DLT tape use block size=5. This work for me. Double the output speed.

[Ayman Altounji]

We also experienced this problem.
What helped at our site was fixing the NIC at 100Mb/half duplex. Make sure the port on the switch and the NIC in the backup server is configured the same way.Ciao, Koen

[Ayman Altounji]

In openserver Use the tape setblk commandThe command:
tape -a 1024 setblk
Will set a fixed 1k block size.

The problem relates to variable block size - there are several articles on the SCO webiste concerning this.

For other operating systems - if you're using a backup software program, check with the vendor - for example arcserve has a configuration file (tapesrv.cfg) that allows setting of block size and other paramaters. More info would be available from the software vendor tech support.