SCO OSR 5: Backup Compression

Tape finished at Fri Dec  2 01:29:16 CST 2005 
last or current transfer: 0k 
Tape started at  Sat Dec  3 01:22:08 CST 2005 
Tape finished at Sat Dec  3 01:29:25 CST 2005 
last or current transfer: 0k 
Tape started at  Sun Dec  4 01:22:07 CST 2005 
Tape finished at Sun Dec  4 01:31:09 CST 2005 
last or current transfer: 0k 
Tape started at  Mon Dec  5 01:22:11 CST 2005 
Tape finished at Mon Dec  5 01:30:52 CST 2005 
last or current transfer: 0k 
Tape started at  Tue Dec  6 01:22:04 CST 2005 
Tape finished at Tue Dec  6 03:48:25 CST 2005 
last or current transfer: 3910830k 
Tape started at  Wed Dec  7 01:22:06 CST 2005 
Tape finished at Wed Dec  7 04:00:40 CST 2005 
last or current transfer: 3927760k 
Tape started at  Thu Dec  8 01:22:07 CST 2005 
Tape finished at Thu Dec  8 03:59:02 CST 2005 
last or current transfer: 3946270k 
Tape started at  Fri Dec  9 01:22:04 CST 2005 
Tape finished at Fri Dec  9 03:53:04 CST 2005 
last or current transfer: 3948990k 

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Fri Dec 9 23:57:57 2005: 1420   dhart


Well, what product or command is used to backup?



Sat Dec 10 00:02:31 2005: 1421   TonyLawrence


And if it isn't one of the Supertars, see (link)






Sat Dec 10 03:23:05 2005: 1425   BigDumbDinosaur


It sounds as though the tape drive in your server is a DDS2 model, which by default, does data compression in hardware using a form of the LZH algorithm. You can verify if compression is enabled with the command "tape getcomp" (don't type the quotes).

The native (i.e., uncompressed) capacity of a DDS2 drive is 4 GB with a 120 meter cartridge, assuming that no soft write errors occur. In theory, LZH can generate 2:1 compression (hence the 4/8 rating for this particular drive), but that is highly dependent on what is being compressed. For example, binary data like bitmaps compresses well, whereas Adobe PDF files don't. Therefore, 1.5:1 average compression is about the most upon which you should rely. Given the 3.9 gigs currently being written to tape, you're still safe with this drive as far as capacity goes. If you start closing in on 6 gigs it's time for a bigger drive (DDS3 is next, 12/24 GB).

I'm also guessing that whatever is performing the backup operation is a front end to cpio. cpio is generally reliable with DDS type tape drives but does not use the drive's resources in the most efficient manner. You might want to take a look at Microlite's Backup Edge software. It works very well on OSR5, takes full advantage of the advanced features of DDS drives, and is easy to install and use. We ship it standard with our servers.



Mon Dec 12 15:11:49 2005: 1429   bruceg


Ditto the Microlite Backup Edge plug. Do yourself a favor, and get it. It is well worth the cost, and will simplify things, and give you a much better piece of mind, while you sleep. I gave up on "custom" backup scripts years ago, and prefer the sane mind I get with Backup Edge. They are also a great customer service oriented company. Your feedback is usually worked into the product, and they take any bug fixes seriously, but for basic backups, there should be no bugs, at least I have never found any :-) It is money well spent, like any good insurance policy.

Good Luck!

- Bruce






Thu Dec 15 16:06:41 2005: 1439   Gantry


I agree with Bruce and APL about using a Supertar to do backups. Scripts are a pain and you never really know if your data is getting backed up. Everything Bruce said about Microedge also extends to LoneTar. We've been using it (and it's wonder airbag/rescue ranger boot restore) for over 15 years now on SCO and Linux systems. We don't sell a server without it, period...

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