How to check a tape media?

[trifo]

Hi!

I have a DDS3 tape drive and some strange things occurring around it:

I tried to create an mksysb backup on a tape but it failed saying "Mount volume 2" as if the tape ended.

Well, I use /dev/rmt0, which is a rewinding device, and the total amount of data is less than the native capacity of the media.

My question is, how to check a tape for surface errors, etc. Is there ready-to-use tool in AiX 4.3 or I need to write some script?

I made up that I would write 100MB garbage files to the tape using dd then reread them and check if OK. Any better idea?

Thanks,

--Trifo

 

[alexhu]

Does it work with another tape ?

Any errors in the error log ?

You can run diags on the device - it does sound as if your getting lots of write retries

Alex

 

[p5wizard]

Perhaps your tape device settings are forcing the backup into a much lower density?

See if

lsattr -E -l rmt0

gives you any idea? Or post its output here. If I remember well, density settings can be 19, 36 or 37 for DDS3. make sure it is at 37 (or your highest possible number - see smit chgtpe and press help on field "DENSITY setting #1") for highest number of gigs per tape

Also an mksysb may be a lot bigger than you think - all mounted rootvg filesystems will be backuped as well... on a nim-server for instance, you will soon end up with a multi-volume mksysb.



HTH,

p5wizard

 

[trifo]

Hi!

Density setting is OK (37). Even though only SOME tape is failing, not all of them. There are 5 tapes used in weekly rotation.

Size manners: there is about 18GB used in rootvg, all mirrored, thus it can not be more than 9GB data to be backed up. Even if mksysb backup is a lot bigger than the amount of data itself (that is not the highest probability) there should be space on the tape.

Error log is empty. The diag did not find any problem. Thus I suspect media defect or some mechanical problem (stiff tape pulley or so).

The question remains the same: any tool to validate a tape media? Like "certify" operation for SSA disks.

 

[MoshiachNow]

Hi,

1.You can checkout the "tapechk" command on :

http://www16.boulder.ibm.com/doc_link/en_US/a_doc_lib/cmds/aixcmds5/tapechk.htm

I do not see much point in using testing scripts here - as long as the errpt is clean of scsi/tape errors (can you please reconfirm it ?)

2.If you have tried only the mksysb - I'd try to "savevg" some big VG,the size that is supposed to fit your tape size.

3.Did you turn on the compression on the tape device?

4.Also,can create a 10GB file using dd and try to dd it onto the tape,see what happens.
To create :
dd if=/dev/zero of=10GB bs=1024kb count=10000

Long live king Moshiach !

http://www.7for70.com/

 

[trifo]

MoshiachNow: yes, I can confirm, error log is empty. No SCSI errors, no TAPE errors, nothing.

tapechk command is used there now, but its purpose is only to read a given amount of files and watch if it succeeds or not. A broken mksysb can greatly result in a succeeding tapechk.

--Trifo

 

[p5wizard]

use the following

(while true; do lptest; done)|dd of=/dev/rmt0 bs=1024

and see how far it goes - at tape end it will tell you how many records of 1K it has written to tape...

Perhaps you have tape cartridges of different length?



HTH,

p5wizard

 

[trifo]

p5wizard: I will try something like this.

Tapes come all from the same box. Thus they sould be equal.

--Trifo

 

[p5wizard]

length in meters should be on tape label or cartridge casing - check anyway.

HTH,

p5wizard

 

[RodKnowlton]

If compression is enabled on the drive, lptest is going to give you a wildly optimistic idea of the capacity of the tape, due to the highly redundant nature of the data.

Either turn compression off and get a look at the true native capacity, or use more representative data.



Rod Knowlton
IBM Certified Advanced Technical Expert pSeries and AIX 5L
CompTIA Linux+
CompTIA Security+

 

[trifo]

Oh, GOD! I've got the problem: it was a Test tape with 11m tape on the pulleys. Grrrr! Jut a sticker label was put on the "Test tape" script. Same box... Eh.

--Trifo