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Tape Libraries and Drives
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35/70

Ayman Altounji
Valued Contributor

35/70

I have a DLT7000 / TZ89N-TA stand alone tape unit backing up an average of 42GB. With compression using NT Backup my 35/70 tapes will give only me the same 40GB of space as my 24/40 tapes. My Compaq service rep installed a softpaq to get me to hardware version 2561. What else can I do to get the 70GB besides use 2 tapes everday for backups?
9 REPLIES
Ayman Altounji
Valued Contributor

Re: 35/70

Did you update the driver to handle the new drive?

DLT4000/7000 Driver for NT
Ayman Altounji
Valued Contributor

Re: 35/70

Are you saying I should update the driver that I already had installed for this?
Ayman Altounji
Valued Contributor

Re: 35/70

Ok, I've updated the drivers - still only getting about 41. I can't out the tape management software on the server because our policy is we keep the isntallation as vanilla as possible. Any other ideas?
Ayman Altounji
Valued Contributor

Re: 35/70

I am having the same problem. I am using ArcServeIT 6.61 on NT 4.0 and for some reason I can only get ~35MB on my 35/70 tapes. In fact ArcServeIT tells me that I am getting a compression ratio of 0.98, so compression is actually hurting me a little bit. And if I try to do software compression, it tells me that it won't because hardware compression is enabled. I do have the latest drivers and firmware installed for my DLT drive -- firmware revision 2255 and drivers version 1.00A.

Any thought are appreciated!
Ayman Altounji
Valued Contributor

Re: 35/70

Just a little update: In Control Panel -> Tape Devices I see that I have a QUANTUM DLT7000. I downloaded drivers from SP10754 and SP12019, but these appear to be identical -- same file size, same creation date. However, on the respective web pages, SP10754 is ver 1.60A, SP13019 is ver 1.00A. Does it matter which driver I use?
Ayman Altounji
Valued Contributor

Re: 35/70

Very important detail all - if you are told you are getting reverse compression (.98 or the like) this usually means you are trying to compress data that is already compressed. This does NOT help and can not be fixed as there is actually nothing wrong...
Ayman Altounji
Valued Contributor

Re: 35/70

I have a similar problem. I am using the 35/70 drive, with Seagate BackupExec 7.2. When my backup was about 50 GB, I was able to put it all on one tape. Now that my data has grown to 65 GB, I am having to use 2 tapes. Any thoughts on how much compression I should realistically be able to get? Should I really be able to to back up 70 GB of data on one tape, or am I asking too much?
Ayman Altounji
Valued Contributor

Re: 35/70

I ran a backup, turning OFF the hardware compression in the DLT drive and turning ON the software compression AND encryption in ArcServeIT. I was able to get all my data on one tape! Unfortunately the ArcServe job log doesn't show how much compression I achieved, (I guess it only does this for HW compression, kinda lame) and my overall average transfer rate dropped from about 200 MB/min to 140 MB/min.

I think the LZ1 HW compression is great--unless you're trying to compress encrypted data. I got a 2.18 compression ration on unencrypted data, but 0.98 when I encrypted. If you're having trouble getting your data to fit on one tape, experiment with your HW and SW compression/encryption settings.
Ayman Altounji
Valued Contributor

Re: 35/70

As a lot of you have noticed - compression is a good discussion point. If data is already compressed, you just can't squeeze too much more. for any drive listed with a capacity of xx/yy - you will never realistically see the 'yy' value - that's under lab conditions (best possible enviornment, etc). if you're getting more than the 'xx' value, it is being compressed - and each installation is going to vary due to what software is in use, what's backed up, etc.