Streaming or not streaming is the question

[Jorgen_2]

It concern DLT8000 and/or LTO drives.
Where are the limit (MB/s) when the drive stops
streaming and or starts? Is there any alogritm how to calculate regarding cache, scsi-type and so on.

[Vincent Farrugia]

Hello,

DLT8000 native speed is 6Mb/s. Compressed (2:1) would be 12Mb/s .

Ultrium drive:

for 215: Native speed is 7.5Mb/s, compressed 2:1 would be 15Mb/s.

for 230: Native speed is 15Mb/s, compressed 2:1 would be 30Mb/s.

HTH,
Vince

[Leif Halvarsson_2]

Hi
HP LTO drives has "adaptive tape speed", this means the drive can slow down the speed if you can't send data fast enough. This is working in a range of about 10-30MB/s (compressed). If you can send data in this range the drive is streaming. This is for the 230 drive, I don't know about the 215.

[Peter Mattei]

Hi Jorgen

Thanks to adative tape speed (ATS) an LTO 230 can stream between 6.1 and 15MB/sec. an LTO 215 between 6.1 and 7.5MB/sec. This is the data rate written to tape.
If compression is enabled and your data is lets say 2:1 compressible your host needs to deliver at least 12.2MB/sec to keep the LTO streaming but you can also write up to 30MB/sec to a single drive.
The DLT8000 is fixed to 6MB/sec data to tape. So again at 2:1 compression you need 12MB/sec to keep it streaming and that's also the max you can achieve.
If you think of SDLT things get even worse. The SDLT 220 has a fixed speed to tape of 11MB/sec and the latest SDLT 320 one 16MB/sec.

See also the very good whitepaper "How to optimize the performance of ultrium tape drives"
http://www.hp.com/products1/storage/products/tapebackup/ultrium_tapedrives/ultrium230/infolibrary/whitepapers/ultperfpress.pdf

More whitepapers can be found at:
http://www.hp.com/products1/storage/products/tapebackup/ultrium_tapedrives/ultrium230/infolibrary/index.html

Enjoy
Peter

[Jorgen_2]

Thank??s guys for all your usable answers!
I think this enough
rgds/jorgen