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Tapes fill up too early

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Each time my backup script runs a Recycle backup the tape appears to fill up prematurely (doesn't appear to happen on incrementals).

 

When Retrospect prematurely demands a tape change, it leaves all the client Macs on overnight waiting for the next member of the set to be inserted.

 

Typically the Configure/Backup Sets/Members would show only 14.4gb is on the tape – actual backed-up data size (as calculated from the Log) correlates fairly closely.

 

The tape length estimate in Configure/Backup Sets/Options is set to automatic. But in any case I would expect Retrospect to fill up a tape before requesting the next member in the set.

 

Can anyone suggest why this is happening and how to fix it?

 

Retrospect 5.1.7 running on G4 733 MHz Mac with 896mb RAM,

backing up a further 6 client G4 Macs to a DDS-3 tape drive (SCSI),

over a 1gb Ethernet network,

onto 5 “day-of-week” Backup Sets with a staggered Recycle.

All Macs running OS 9.2.2

 

Many thanks in anticipation.

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(1) how big (capacity) is the tape?

 

(2) what is the total data capacity of the 6 clients plus the computer running Retrospect?

 

(3) you are aware, aren't you, that a "recycle" will, on its first backup, back up ALL the data on all of the machines? (see (1) and (2) above).

 

You may be seeing the expected behavior, and might need to move to autoloader technology (or another tape technology such as VXA or LTO) for bigger capacity.

 

You can also set the media timeout to give up after some amount of time.

 

Russ

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Thanks for responding, Russ.

 

1) Retrospect estimates tape capacity at 23.5 gb, the drive has hardware compression.

 

2) Disk capacity of all 7 Macs totals 490gb, BUT Retrospect only looks at 2 particular folders on each Mac - those folders total 19.5gb.

 

3) Yes, I am aware.

 

So, to my way of thinking, if there’s only 19.5gb of data (before the tape drive even does it’s hardware compression) it should all fit on one tape during a Recycle backup, err, shouldn’t it? :uncertain:

 

 

PS: Will media timeout shut down the host & client Macs?

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Quote:

1) Retrospect estimates tape capacity at 23.5 gb

 


Sadly, that doesn't mean much. It just reports whatever number you have filled in for "Configure > Backup Sets > Configure > Capacity" (if you have changed it from "Automatic"). We haven't had much luck with that - "Automatic" on our 160 GB (compressed) VXA-2 tapes always shows 1K available regardless of amount used. We see about 110 to 120 GB actual on our usage, which has lots of small files (which lowers capacity). I checked a moment ago, and DDS-3 tapes seem to be rated about 24 GB (compressed), which will only be seen if you have big files that are compressible (so that Retrospect can keep the drive pumped with data without starving); if your experience matches ours, then you will probably get about 17 GB per tape (70% of compressed rated capacity). We saw similar percentages when we used DDS-2 on ASIP with Retrospect. Actual numbers depend on the mix of large/small files, compressability of the files, and whether you have enough processor and I/O bandwidth to keep the tape drive channel fully primed.

Quote:

2) Disk capacity of all 7 Macs totals 490gb, BUT Retrospect only looks at 2 particular folders on each Mac - those folders total 19.5gb.

 


If that's 19.5 GB for all 7, then that's just slightly above what will be seen for each tape with real-world files and typical compression.

 

Marketing types tend to use optimistic numbers that require artificial conditions to reproduce.

 

Quote:

PS: Will media timeout shut down the host & client Macs?

 


It won't shut down the clients. What happens on the Retrospect host depends on how you have your "Run Control" and "Unattended" preferences set.

 

I'll make a suggestion if you want to continue the current path without an autoloader: Since the numbers are so close, why not back up 6 of the clients on the recycle (first) day, then do all 7 incremental the next (and following) days on a different (erased) tape that will be appended as a member of the backup set. The incremental on the missed client will become a full backup the first time, and the others will be true incrementals.

 

But you really might want to consider an autoloader. It changes your whole view on things, and you will wonder why you never had one before. Exabyte has really dropped the price on their VXA-3 1u drives with 10 slot autoloader. Their entry level unit (VXA-172, LVD SCSI, $1662 (USD) at PC Connection) is field-upgradable (by entering a license code) to one with double the capacity (VXA-320) when your capacity needs increase. We are very happy with our VXA-2 1x10 1u LVD SCSI, plan to get the field upgrade kit to VXA-320 (will pay for itself in a few months because of double capacity on the tapes).

See Exabyte VXA drives

 

I don't know whether your version of Retrospect supports this drive, don't know whether your SCSI is LVD; Retrospect 6 does support the drive and autoloader nicely.

 

Hope this helps.

 

Russ

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I have the same problem with my VXA 320 drive... it only uses half the tape (X23) then asks for a new one.. So I now have 11 half filled tapes that I paid full price for.

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