[opensuse] Linux and Sony DDS Compression
I am using at Sony DDS3 SDT-9000 with 125M DDS3 tapes. I have set the hardware DC switch to perform hardware compression. I have used mt to set datcompression on. I do not seem to be able to write over 12MB on the tape. I would exprect more if compression is working. Is this a problem that other list members have encountered and solved? I'm using SuSE Linux 9.0 (2.4.21-286-smp4G) -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
On Wednesday 07 March 2007 15:53, Rejaine Monteiro wrote:
I do not seem to be able to write over 12MB on the tape. I would exprect more if compression is working.
12MB? I doubt that... a typo? I have a SDT9000 that I don't use anymore but in my experience, the best you can expect with compression is about 1.6 times the capacity of the tape. Thus on the 12GB tapes you are using, you could expect about 19GB on average data. If you are compressing the data before you write it, expect a lot less. And I never had to turn the compression ON... that may be your problem. The DAT drives usually compress by default and you may have foiled that. Give it a try. -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
On Wednesday 07 March 2007 15:22, Bruce Marshall wrote: On Wednesday 07 March 2007 15:53, Rejaine Monteiro wrote:
I do not seem to be able to write over 12MB on the tape. I would expect more if compression is working.
I have a SDT9000 that I don't use anymore but in my experience, the best you can expect with compression is about 1.6 times the capacity of the tape.
Thus on the 12GB tapes you are using, you could expect about 19GB on average data. If you are compressing the data before you write it, expect a lot less.
And I never had to turn the compression ON... that may be your problem. The DAT drives usually compress by default and you may have foiled that.
This has occurred with different tapes? The tape drive is clean? Your system can stream data fast enough to keep the tape drive occupied? You are not compressing the data in software before writing to tape? How did you set the compression jumper on the drive? If the jumper is set the host controls compression, if the jumper is open the drive sets compression on and it cannot be changed by the host. What data are you backing up? I could not get much more than 13 GB on my backup; much of it was mp3 and jpg files, so compression would be expected to be very low. Sony provides a utility to test the tape drive; one of the tests will set compression. AFAIK, you cannot test compression with the Sony utility, HP's LT&T will test compression, but may not work on a non-HP drive. You might also set the density code with mt, DDS3 is set to 25, e.g. mt -f /dev/st0 setdensity 0x25 -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
At 07:53 AM 8/03/2007, Rejaine Monteiro wrote:
I am using at Sony DDS3 SDT-9000 with 125M DDS3 tapes. I have set the hardware DC switch to perform hardware compression. I have used mt to set datcompression on.
I do not seem to be able to write over 12MB on the tape. I would exprect more if compression is working. Is this a problem that other list members have encountered and solved?
is this a new drive and you are using the tape supplied with the drive??? i've found that the tape supplied is only for a trial/testing and as such are not full length, only about 10meg of tape was on mine. depending on what you are storing, trying to compress raw/pure data can have the reverse response, has something to do with the compression algorythm. also these drives have by default compress turned ON, are you sure you didn't turn it off instead. also, what was the operating system the drive was setup for when you received it? you may need to change these switches to default rather than specifics. ideas to check scsijon -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 268.18.7/712 - Release Date: 6/03/2007 3:42 PM -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
participants (4)
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Bruce Marshall -
Rejaine Monteiro -
scsijon -
Wade Jones