Tape Libraries and Drives
cancel
Showing results for 
Search instead for 
Did you mean: 

density code of sdlt220 and compression code 16

SOLVED
Go to solution
Carmela Agustin
Occasional Advisor

density code of sdlt220 and compression code 16

anybody knows the density code in decimal of sdlt220 drive?

when i do:
mksf -d stape -I 0 -b 147 -c 16
...what is 16? are there different compression codes? what is the best compression code i can use for an sdlt220 drive?

with this command, i was able to create:
/dev/rmt/c2t9d0D147C16
but when i tried using it with:
tar -xvf /dev/rmt/c2t9d0D147C16 /tmp
there's an error:
tar: cannot open /dev/rmt/c2t9d0D147C16
what can i do so i can use this?
12 REPLIES
Mugilvannan
Valued Contributor

Re: density code of sdlt220 and compression code 16

Hi,
To knw the density code of ur drive try http://sunsolve.sun.com/search/document.do?assetkey=1-9-30-1

To knw the mksf in details, http://docs.hp.com/en/B9106-90008/mksf.1M.html

I hope Sony SDLT1-320 is the best for sdlt220 drive.

And about query on tar: cannot open plz visit http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=954268

Thanks,
Mugil
If U need a helping hand, U will find one at the end of your arm
Scott McIntosh_2
Honored Contributor

Re: density code of sdlt220 and compression code 16

Depends. You can either specify the density setting for the mode select and control compression via the data compression page, or use alternative density settings that predefine the compression.

SDLT220 format is 0x48, but you can also use 0x90 (compression off) or 0x91 (compression on), although the latter are not preferred by Quantum according to the SDLT220/320 SCSI Reference Manual (anyone can read it on Quantum's web site).

147 decimal is 0x93, which is SDLT320 format (compression on). So if you have a SDLT220 drive, not sure why you'd be using that density value. It can't write SDLT320 format.

As for the compression field, when compression is used, you have to specify which compression algorithm should be used. Maybe back in the dark ages, devices actaully had multiple algorithms, but in the 21st century, everything I've ever seen only supported one algorithm. For SDLT220, that's 0x10, or 16 decimal, the only valid value for that setting. That's why -c 16.

Now, is the -c 16 necessary since you specified a 0x9? density code rather than 0x48? I don't know. Guess it can't hurt.

Thanks,
Scott
HP Support
Carmela Agustin
Occasional Advisor

Re: density code of sdlt220 and compression code 16

Dear Scott,

Thank you very much for your explanation! It really helped a lot since I've been trying to find these information in the internet (and so far, I did not get anything close to your answer). Anyway, since I'm using SDLT220 drive, what is its equivalent density code? Or what can I use? So that when I do mksf again, I can specify this in the -b option. Thank you very much again.

Regards,
Carmela

Carmela Agustin
Occasional Advisor

Re: density code of sdlt220 and compression code 16

Just to clarify, I'm creating a new device file for the sdlt220 because the existing or defaults, when I used it, it does not do compression. So my backup is always on the native capacity of the sdlt220 (it is actually not compressing even at the very least).

What density code can I use so that my sdlt220 drive will do compression? If 147 is for sdlt230, what is for the sdlt220?

Thanks again.
Leif Halvarsson_2
Honored Contributor

Re: density code of sdlt220 and compression code 16

Hi,

Are you sure that the problem is related to the devicefiles. I have not used any SDLT drives myself but, for all types of drives I have tested, the default device files (created automatic at reboot or using the insf command) are compressed.

Is perhaps your backup data already compressed or, is compression disabled in the drive (don't sure if that is possible with sdlt driver).

Which OS version are you using ?

Scott McIntosh_2
Honored Contributor

Re: density code of sdlt220 and compression code 16

145
Carmela Agustin
Occasional Advisor

Re: density code of sdlt220 and compression code 16

Thanks Scott.

Hi Leif,
I already tried using the default device files but unfortunately, I didn't get the compression (not even 1%). My backup software already is set to compress = hardware. I'm saving 140GB of data, but only less 110GB can be save into the SDLT1 tape. The 140GB of data should fit into 1 SDLT1 tape right? Would you know how can I check if the compression of the tape drive itself is "active" or turned on?

Before I bought this sdlt220, I was using a dlt8000 drive and I had no problems. But since my data now is more than 80G, I decided to buy an sdlt220.

Thanks very much!
Carmela Agustin
Occasional Advisor

Re: density code of sdlt220 and compression code 16

By the way, my OS is B.11.23; my server is HPItanium (HPIA64).

From the manual of the sdlt220, it says the compression is defaulted to "on".

I created a device file from Scott's 145 density and I was able to test the tar command to that drive successfully.

Thanks very much again.
Carmela Agustin
Occasional Advisor

Re: density code of sdlt220 and compression code 16

Hi to all,
My problem has now been solved; I was able to backup using the sdlt220 and it is compressing. The answer that solved this is Scott's 145 density. Thank you very much for all your help.

Carmela Agustin
Occasional Advisor

Re: density code of sdlt220 and compression code 16

Hi Scott,
How can I assign that this message has been solved by you? Can you pls reply again so I can assign 10pts and close this issue? Thanks very much again!
Scott McIntosh_2
Honored Contributor
Solution

Re: density code of sdlt220 and compression code 16

Not a problem. You can usually look in /usr/include/sys/mtio.h to find the density codes stape knows. Small problem this time is that on IA-64, the entry for 220GB compressed (2:1), ie SDLT220 format with compression on, is actually mistyped. It says 100GB uncompressed and 200GB compressed, and that's wrong. So a bad example in this case. But, you see the value for 220GB compressed is 0x91 hex, which is 145 decimal. Thus your -b value for mksf.

As for the -c value, you really have to look at the "SCSI Reference Manual" for the drive, which you should be able to obtain from the drive vendor. For SDLT220/SDLT320, the only allowed value is 0x10, or decimal 16.

Thanks,
Scott
HP Support
Carmela Agustin
Occasional Advisor

Re: density code of sdlt220 and compression code 16

Scott McIntosh was able to solve my inquiry about the density code of sdlt220 and now I can do backup from the said drive. Thank you.