We are running Backup Exec 12.5 and have recently moved from LTO-3 to LTO-4. All works fine except for the tape capacity. All the data is precompressed so we do not expect more than 800GB but tapes are being ejected at between 600GB and 650GB during backup as full! For example, with new HP media, looking at the statistics, the following is reported: Used capacity: 780GB Bytes written: 584GB Bytes read: 192KB Mounts: 4 Seeks: 15 Errors: All 0 Ideas? Thanks Michael

Received a replacement drive. Works perfectly and gives full capacity with BE 12.5 and HP Tape Tools. Compression on/off with already compressed files not an issue

Hi, I assume you are using the Symantec drivers installed for the drive? if not, use tapeinst.exe to install the Symantec drivers. also doesn't hurt to ensure that the drive itself is on the BE 12.5 HCL! thanks!

I suspect you have a clogged tape drive head. I suggest running vendor diagnostics on the drive and working with the hardware vendor. http://www.symantec.com/docs/TECH193200

All the data is precompressed When you compress data which are already compressed, you will probably end up with more data than what you have started with. See my article below for an explanation https://www-secure.symantec.com/connect/articles/compression-short-explanation Since the data is already compressed, you might get better result if you turn off compression.

If the data is pre-compressed ensure no hardware compression or encryption is used in the Job. Without software/hardware compression/encryption are you able to accomodate all data in one tape. If you still face the problem better perform hardware diagnostics on the Tape Drive and Tape as well.

Thank you for confirming what I have said. Do read this https://www-secure.symantec.com/connect/forums/paraphrasing-answers

LT0-4 Tape Capacity Problem

14 Replies

CraigV
Moderator
12 years ago
Hi, I assume you are using the Symantec drivers installed for the drive? if not, use tapeinst.exe to install the Symantec drivers. also doesn't hurt to ensure that the drive itself is on the BE 12.5 HCL! thanks!
Larry_Fine
Level 6
12 years ago
I suspect you have a clogged tape drive head. I suggest running vendor diagnostics on the drive and working with the hardware vendor.

http://www.symantec.com/docs/TECH193200
pkh
Moderator
12 years ago
All the data is precompressed

When you compress data which are already compressed, you will probably end up with more data than what you have started with. See my article below for an explanation

https://www-secure.symantec.com/connect/articles/compression-short-explanation

Since the data is already compressed, you might get better result if you turn off compression.
Gurvinder
Moderator
12 years ago
If the data is pre-compressed ensure no hardware compression or encryption is used in the Job. Without software/hardware compression/encryption are you able to accomodate all data in one tape. If you still face the problem better perform hardware diagnostics on the Tape Drive and Tape as well.
pkh
Moderator
12 years ago
Thank you for confirming what I have said. Do read this

https://www-secure.symantec.com/connect/forums/paraphrasing-answers
Michael_Strelit
Level 3
12 years ago
Just back from vacation. Thanks for all the comments.

1. Using HP 1840 SCSI with Symantec drivers so no problem there.

2. LTO-3 tapes backup the full 400GB and fast (in the above drive). Much faster than in an HP LTO-3 drive.

3. Hardware compression turned off or on makes no difference.

When writing to an LTO-4 tapes is a different head used?
CraigV
Moderator
12 years ago
Not unless you have an LTO3 drive and an LTO4 drive in the same library. A tape head is a tape head.

Under the Media tab, check to see if any of the LTO4 tapes have excessive Hard Write Errors which could indicate a problem with the tapes.

Also, download HP Library and Tape Tools (HP LTT) from the HP website, stop the BE services and run the diagnostic check against the drive. You are interested in the compression test, and the Write/Read tests on the LTO4 tapes. The tape needs to be manually inserted via LTT first, and it must be overwritable.

Thanks!
Michael_Strelit
Level 3
12 years ago
Have installed Tape Tools and run a number of tests - all passed and no problems I can see.

Ran another test backup today. BE Monitor reported 711GB stored and ejected the tape as full (there was 770GB to backup). Media properties showed 663GB written and 780GB used capacity! The media contains no other backups. The data rate is 5400MB/min which is good. Compression is off (1:1) and there were no hardware or software errors reported.

Why am I still missing 70GB of storage space? Is this a BE 12.5 issue?
Larry_Fine
Level 6
12 years ago
I stand by my original hunch. For whatever reason, clogged heads don't seem to reveal in normal diagnostics. Have you opened a case with HP support?

I suspect you have a clogged tape drive head. I suggest running vendor diagnostics on the drive and working with the hardware vendor.

http://www.symantec.com/docs/TECH193200
pkh
Moderator
12 years ago
It can also be a tape with a lot of bad areas so it has less capacity. Have you tried with a brand-new tape and observed the written capacity and the number of errors. A new tape with a high number of errors usually indicates that the tape drive is faulty.