When I encounter tapes that are marked as full when the amount backed up
is less than the tapes native capacity, then there are several things I
suspect:

1.) Slow write rate due to slow backup push from clients (bottleneck
could be load, not enough bandwidth, network traffic, etc) or slow
network interface on backup server. If you are using copper over
Ethernet than at best you will get from 10MB to 35MB throughput. Because
of hardware compression the pipe from Ethernet to SCSI funnels open. I
average 40MB/s write speed and have sustained 50-60MB/s write speeds on
backups jobs of clients that are using GHz adapters.

2.) Not enough data is being pushed to tape. LTO is a streaming
technology.  Data is written in a linear fashion forward.  If you can
push enough data to tape to keep it from "shoe shining" or "backhitch"
which is the term applied to the process of tape drives having to slow
down, stop, write file mark; start, look for correct position on tape
(wind forward and wind backward until the correct file mark is found)
and continue repeating this process over the course of backup. This can
cause drive head damage and it definitely damages tapes. Networker being
the intelligent backup product that it is senses this and will mark a
tape as full to prevent you from using it.

3.) Damaged tapes due to physical handling, dust, etc or tapes damaged
by reason number two.

4.) Your drives could be dirty.

Suggestions:

1.) When you look at your save set messages, look for aborts in the
status and in the flag (ca,ta,etc). It only takes a couple of problem
clients to kill the overall backup job.

2.) If your hardware supports make sure Tape Alert is enabled. Networker
will display the warnings in its logs.

3.) Also block size relates to performance which in turn has an effect
on tape capacity. I configured my backup server's OS to accept a larger
block size than the 64K windows default. The Legato Performance Tuning
Guide has some good information on testing and tuning.

4.) Trying using just one or two drives. I backup 3.5TB daily and I use
1 drive per backup server though each Server has two LTO-2 drives. Only
on 1 Server do I use both drives. I try and strike a balance leaning in
favor of heavier multiplexing. 

Thanks,

Dana

-----Original Message-----
From: Legato NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU]
On Behalf Of rrevuru AT GMAIL DOT COM
Sent: Friday, March 24, 2006 12:14 PM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: Re: Networker Newbie

On 3/24/06, Greggs, Dana <c-dgreggs AT state.pa DOT us> wrote:
>
> When a tape is loaded into the drive, execute the following command 
> ("mt -f" followed by your tape drive path) to see if hardware 
> compression is
> enabled:





Dana: This is what i see, for some reason i see there is atleast 60GB
worth of space is unaccounted for, and the Volume=Full status. And if
you guys take a look "Compression Enabled" on my tape drives i believe.

1. Is this problem troublsehootable?
2. Does it matter the data i am backing up, i am backing "File Server"

mt -f \\.\tape0 stat


Media Capacity  = 204.90GByte
 Media Remaining = 148.50GByte
 Media Blocksize = 0
 Media Partition Count = 0
 Media is not write protected
 default blocksize = 32768
 maximum blocksize = 65536
 minimum blocksize = 2
 MaximumPartitionCount = 0
 Partition = 0
 Logical block position = 1
 EOTWarningZoneSize = 0
 Error Correction Enabled
 CompressionEnabled
 Features:
  Performs SHORT erase operation
  Performs LONG erase operation
  Performs IMMEDIATE erase operation
  Can report maximum tape capacity
  Can report amount of tape remaining
  Support FIXED block length mode
  Support VARIABLE block length mode
  Returns errors on write if tape is write - protected
  Performs Hardware Error Correction
  Supports hardware data compression
  Can provide current absolute device block address
  Can provide current logical block address and partition
  Can physically load and / or unload tape
  Support PREVENT / ALLOW Media Removal
  Performs IMMEDIATE rewind operations
  Allows Setting FIXED LENGTH or VARIABLE block sizes
  Performs IMMEDIATE Load / Unload operations
  Allows hardware data compression to be enabled / disabled
  Can position tape to an absolute physical block
  Performs IMMEDIATE absolute block positioning
  Can position tape to a logical block(and partition)
  Performs IMMEDIATE logical block positioning
  Can position tape to END of RECORDED DATA
  Can perform tape record positioning(backwards / forwards)
  Can perform tape file positioning(backwards / forwards)
  Can move backwards across records or filemarks or setmarks
  Can write FILEMARKS
  Performs IMMEDIATE tape mark write operations

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