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HP LT03 Ultrium Tape

Occasional Contributor

HP LT03 Ultrium Tape

Good Afternoon

I am no longer able to back up 580Gb to a HP LT03 Backup Tape. We run Backup Exec 12 for Windows Servers and have the compression set in order to allow a 400Gb tape to in reality become an 800Gb tape. However, recently we are unable to successfully backup without the application asking for a second tape, which it does during the night and so eventually times out and cancels.

The problem isnt with the application as I have spoken to Symantec.

The problem lies with the 2:1 compression ratio on the HP LT03 tapes.

Can someone please tell me why a 400Gb tape will not back up my 580Gb of data when using tape compression? I have read on another thread that it may be down to compressed files being backed up to a compressed tape. Could this be a reason?

i look forward to your reply.
Acclaimed Contributor

Re: HP LT03 Ultrium Tape

>> ... in order to allow a 400Gb tape to in reality become an 800Gb tape

This is marketing, but not true. Don't believe this.

In fact there is a native space of 400GB, not more. The compression ration depends on the type of data. IMHO it is somewhere between 1:1 and 1,2:1 usually.

If you assume a ratio of 10:1, then you can even store 4TB on such tape - LOL!


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Occasional Contributor

Re: HP LT03 Ultrium Tape

Thank you for your reply!

When you mention "the type of data" can you please expand on this?

We are backing up an Exchange mailbox, Microsoft Office files, Jpegs, Pdfs, Photoshop files, CAD drawings and assemblies, a whole lot of files are being backed up but this has never been an issue until the last couple of weeks or so.

Curtis Ballard
Honored Contributor

Re: HP LT03 Ultrium Tape

If the total data set size hasn't changed significantly it is possible that a larger percentage of the data set is compressed or it could be that your drive needs cleared or the drive or tape is worn and has to perform too many rewrites to achieve the required signal quality on the writes.

If you use HP Library and Tape Tools ( and pull a support ticket from the drive following a backup one of the field it reports is the actual compression ratio you achieved. It will also show if there is capacity loss due to rewrites being required.
Valued Contributor

Re: HP LT03 Ultrium Tape

Chrism70, the 400GB tape must be a LTO2 media. You can backup 400GB assuming you have set 2:1 compression.
You cannot go more than 400GB. If you havent set 2:1 compression, than you wont be able to backup anywhere near 400GB as per Torsten.
Looks like you'll use 2 tapes for backing up 580GB.
Richard Bickers
Trusted Contributor

Re: HP LT03 Ultrium Tape

As Curtis says, you should be able to see what's going on (low compression ratio or a drop in drive margin) from an LTT support ticket. Just pull the ticket first thing in the morning after the backup has timed out.

If you want any help understanding the ticket then just post it here and we'll take a look.

My guess would be you've increased the amount of pre-compressed data (all those media files) and that type of data won't compress any more.

2:1 is considered an industy average for a likely compression ratio but with the increase in media files these days that number is coming down over time. You should be able to see what you're actually getting with LTT.
It's more interesting when it's gone wrong
Occasional Visitor

Re: HP LT03 Ultrium Tape

We had something similar recently - backup that used to fit one one tape started asking for a second. Turned out to be a faulty tape drive, too many rewrites. Swapped out to a spare unit and now the backup fits again.