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Tape Libraries and Drives
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Streaming or not streaming is the question

Jorgen_2
Occasional Contributor

Streaming or not streaming is the question

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.
Jorgen Krantz
4 REPLIES
Vincent Farrugia
Honored Contributor

Re: Streaming or not streaming is the question

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
Tape Drives RULE!!!
Leif Halvarsson_2
Honored Contributor

Re: Streaming or not streaming is the question

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
Honored Contributor

Re: Streaming or not streaming is the question

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
I love storage
Jorgen_2
Occasional Contributor

Re: Streaming or not streaming is the question

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