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тАО12-06-2006 02:05 PM
тАО12-06-2006 02:05 PM
Another compression Q on storageworks DAT72 ntbackup
I have an SBS 2003 HP Proliant G4p whatever server with internal HP Storageworks USB DAT72 tape drive.
I believe its model C7438A serial number HU10609W1Z (saw that somewhere but being internal makes it hard to verify).
It should have a 72GB capacity but is capping or crapping out at 43GB which is causing grief for my backup strategy.
Tape drive properties indicate capacity is 38GB and compression enabled is false.
HP website says to use their drivers rather than MS drivers. Server was using their driver hpdat.sys version 1.5.3.1 and is now using new version 1.5.3.2. I upgraded driver but to no avail.
NTbackup is set up to use hardware compression but everything indicates hardware compression is not happening.
I have also downloaded HP L&TT and tried to do the configure thing (set compression) but that test (I would call it a configuration change myself) failed.
I emailed this issue to HP online support two days ago and still waiting, waiting....
I have read through the forum on tape drives with compression problems and could not see an answer.
I am aware NTFS may already compress my files and that I should not expect 2:1 compression but I'll believe that when I see my hardware compression enabled and compression happening.
Not too excited about pulling my server apart to check DIP switches (could kill that IT salesman for selling me an internal drive!).
Is there an easier way to resolve this gremlin. Surely after 4 years and 4,000 forum questions on hardware comression HP have a comprehensive analysis on what is needed and a utility to KISS-fix it. It can't be that hard.
This is the fourth problem in lack of support on HP products I have suffered in as many months and its starting to seriously annoy me.
Davown
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тАО12-07-2006 01:02 AM
тАО12-07-2006 01:02 AM
Re: Another compression Q on storageworks DAT72 ntbackup
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тАО12-07-2006 09:14 AM
тАО12-07-2006 09:14 AM
Re: Another compression Q on storageworks DAT72 ntbackup
Since yesterday's post, I have:
- done LTT compression test - passed.
- done LTT Test - Drive Config disable compression - passed
- done LTT Test - Drive Config ensable compression - failed
- pulled server apart and can find no DIPs
- pulled plug out of internal DAT72 drive and restarted it (power down in effect);
- DAT72 properties reported Compression Enabled - TRUE
At last I thought I was getting somewhere. Seemed DIPs or no DIPs my DAT72 was resetting to correct default position and compression was possible BUT:
Why does LTT compression enable fail?????
Then:
- I started ntbackup but cancelled it after 30 minutes;
- checked DAT72 properties and they were stuffed again Compression Enabled - False
I get the impression ntbackup resets the compression to OFF after a backup stops. Hopefully this means that ntbackup sets compression to ON when it starts a backup but there is no way of checking this apart from emperical backup volumes.
Given my tapes are capping out at 40GB on a DAT72, the emperical result suggests compression is not happening, or as you allude, DAT72 hardware compression does little on an NTFS server.
So the conclusion I am reaching is that HP marketing blurb has misled both myself and the IT consultant who recommended the DAT72 for my 80GB server. It would appear the DAT72 is only going to provide 50% solution to my backup needs.
As Shania Twained: "That don't impressa me much"
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тАО12-08-2006 12:01 AM
тАО12-08-2006 12:01 AM
Re: Another compression Q on storageworks DAT72 ntbackup
It seems to me that NTbackup is turning hardware DC off not on. To my knowledge it doesn't leave it off by default. I just looked at the parameter list for NTbackup and it does say HC - hardware compression - pretty clearly so that's odd to me. I'd expect to see the LTT support ticket show DC enabled even after you cancel the backup. You could try some real quick backups with different options to see if you can get it to stay on.
You should be able to pull a support ticket with LTT immediately after the backup and it will tell you what the compression ratio has been since the tape was last loaded. If hardware compression was off you'll get 1:1, if it was on but trying to compress data that is already compressed then it will actually expand. You'll get something like 1:1.2. If it's compressing normally you'll get anywhere between 1.3:1 and 100:1 (empty DB).
We quote 2:1 as an average which is reasonably accurate for an average but obviously not what you'll get if the data is already compressed. I'm afraid everyone in the industry does that and we have to be consistent. There's a lot of confusion over compression ratios but what you get really boils down to what you're compressing and that could be anything.
One other thing you could try is to run the device performance test using 2:1 compressible data to the end of the tape. That will at least confirm you can get about the right amount of compressible data onto one tape. Won't help if you can't turn it on or have pre-compressed data though.
The LTT enable compression config (test) shouldn't fail. We'd like to know more about that. Could you please find the EventLog.ltt file in the LTT install directory to LTT.team@hp.com please? This is the LTT support mailbox.
I agree, this is a utility rather than a test but for the time being they're all together under one list. We'll fix that in a future release.
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тАО12-08-2006 09:47 AM
тАО12-08-2006 09:47 AM
Re: Another compression Q on storageworks DAT72 ntbackup
Not sure where the LTT support ticket is but I will look for it in LTT on Monday. Being in Oz, there is a bit of a time differential in play here.
Glad to have your assistance and happy to work with you towards resolving this issue. Hopefully the attached logs tell you something but from my experience of troubleshooting PCs they rarely do.
Davown
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тАО12-08-2006 10:51 AM
тАО12-08-2006 10:51 AM
Re: Another compression Q on storageworks DAT72 ntbackup
I assume your attachments went to the LTT support mailbox so I've asked them to look out for them. Hopefully you'll get some communication w.r.t. finding out why LTT can't set compression on in your drive. I'd like to get to the bottom of that one.
That may be a different issue to what's going on with NTbackup. That's a mystery all by itself. I know people use NTbackup successfuly with our drives so there's something amiss here.
It would be worth checking your file system settings to see if you've already got compressed files. I've not seen anything in the documentation but it's widely known that trying to re-compress data that's already compressed can lead to expansion (there's a little overhead with compression that is *usually* offset by the final size reduction) so it may be that NTbackup automatically turns of hardware compression if it knows the files are already compressed - whatever you set your parameters to. That's just a guess, mind, but it does fit the symptoms.
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тАО12-10-2006 03:45 PM
тАО12-10-2006 03:45 PM
Re: Another compression Q on storageworks DAT72 ntbackup
The support ticket indicates that compression is disabled but does not id why. Perhaps it's ntbackup causing this problem, or perhaps another.....
I would be surprised if its another application interfering with DAT72 comression settings as our server is relatively new (6 months old) and I have a preference to minimise conflicts.
From my knowledge, compression has never worked on our server although this only became obvious about 3 months ago when our backups started to exceed 36GB.
Davown
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тАО08-23-2007 12:35 AM
тАО08-23-2007 12:35 AM
Re: Another compression Q on storageworks DAT72 ntbackup
When I test DAT72 with LTT, it pass all test (2:1 ,3:1 compression) but I get warning massage that last backup was at 1:1 compression. Could it bee NTbackup problem, or can I do something with DAT72?
Predrag
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тАО11-06-2007 12:37 AM
тАО11-06-2007 12:37 AM
Re: Another compression Q on storageworks DAT72 ntbackup
Using SBS2003 and HP Storageworks DAT72 USB internal drive.
I have had a backup exceed 36Gb but only just. Could it be that NTBACKUP is actually trying to backup to DDS4 media and not DAT72? DDS4 media is 20/40Gb.
Did you ever resolve your issues?
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тАО04-22-2008 05:57 AM
тАО04-22-2008 05:57 AM