Nico,

I run LTO 1 and now some LTO 2 drives.  We use client side compression
so hardware compression is turned off.  I usually get 103GB to 104GB on
a tape.  My tapes are nearly always written as clones from a adv_file
disk devices.  We back up to disk, then clone and stage to tape to
make two copies.

If I overstretch the disk drives feeding the tapes, the tape drives
start writing at a slightly lower speed.  This also happens if I am
backing up direct to tape from clients that cannot keep the drive
streaming.  This will cause the tape to get lower utilisations.
Usually this is only a few percent, 102GB down to high 90s.  Tape
errors however cause much more significant reductions in capacity
depending on where the error occurs.  I reckon on not recycling these
tape.  The last save set on these tapes is usually marked "suspect".

I was told once that the drives have two methods of coping with data
not being received fast enough.  One is to stop, back up and start
again (this often known as shoe shining).  The other method is to add
some padding somewhere (the details were not explained to me), but I
assumed it was in inter-record markers.

Tim.

On 16/08/2006, at 9:41 PM, Nico De Ranter wrote:

On Wed, 2006-08-16 at 08:48 +0100, Wood, R A (Bob) wrote:

Nico,

Networker will flag a tape as full if it has a write error on that tape. It doesn't matter what caused the write error (physically reached end of

tape, dirty drive, lumpy power supply, SCSI resets, etc.) Networker's
response is to mark the tape as Full and move on.

That's what I was afraid of. However somehow I would have expected

Networker to flag the tape as bad in stead of just moving on to the next tape. I've got 1 tape device which sometimes writes at a very low speed, I'm keeping an eye on it. Of course since the moment I decided to keep

an eye on that drive it works perfectly at full speed. It knows, I'm
sure it knows...

Thanks

Nico

As you're getting quite a few of these you may wish to try a bit of
investigating yourself (were the tapes written on the same drive? Are
there any messages in the system log that correspond to the time that

the tapes were marked full? If connected via fabric, any messages on the switch?)sort of thing. Try to find out if it is tape drive, connection

or media related.

Whether you crack it or not, you'll know a little more about your setup

than when you started (and that's no bad thing)  :)

Regards
Bob

-----Original Message-----
From: Legato NetWorker discussion
[mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU] On Behalf Of Nico De Ranter
Sent: 16 August 2006 08:27
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: [Networker] Not all tapes are fully used

Hi,

I'm using LTO-1 tapes that can hold up to 105GB. I just
noticed that many of my tapes that are labeled 'full' in the
volumes overview are only partially used e.g. only about 80GB
or in some cases even 18GB is used but the tape is labeled as
'full' anyway. Is does normal or does it look like I have a
problem with one of my tape devices?

Nico

--
Nico De Ranter
Senior System Administrator
Sony Service Center (NSCE)
The Corporate Village, Da Vincilaan 7-D1
B-1935 Zaventem, Belgium
Telephone: +32 (0)2 700 86 41 Fax: +32 (0)2 700 86 22

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--
Nico De Ranter
Senior System Administrator
Sony Service Center (NSCE)
The Corporate Village, Da Vincilaan 7-D1
B-1935 Zaventem, Belgium
Telephone: +32 (0)2 700 86 41 Fax: +32 (0)2 700 86 22

To sign off this list, send email to listserv AT listserv.temple DOT edu and type "signoff networker" in the body of the email. Please write to networker- request AT listserv.temple DOT edu if you have any problems wit this list. You can access the archives at http:// listserv.temple.edu/archives/networker.html or

via RSS at http://listserv.temple.edu/cgi-bin/wa?RSS&L=NETWORKER

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