How to do multiple Informix exports to a single tape ?

[JGD_1]

Would anyone know how to export several databases on one tape (approximately 20 Go in 12 databases to one DDS3 tape) ?

Apparently tar and cpio are limited to 2 Go and dbexport only exports 1 database to a tape.

I read a lot on fbackup. Is there a possibility ?

Any other tries will be welcomed !

[James R. Ferguson]

Hi:

Several comments.

I'm not familar with Informix and its inherent backup schemes. However:

1. fbackup does support files that exceed 2GB (largefiles) whereas tar and cpio do not.

2. Oracle handles the export of very large databases by splitting its export processes into background pipes into multiple filesystems. The thread that describes this, and that references the Oracle document is:

http://my1.itrc.hp.com/cm/QuestionAnswer/1,1150,0xcc4668c57f64d4118fee0090279cd0f9,00.html

Hopefully this will assist you. Good luck.

...JRF...

[James R. Ferguson]

Hi:

Several comments.

I'm not familar with Informix and its inherent backup schemes. However:

1. fbackup does support files that exceed 2GB (largefiles) whereas tar and cpio do not.

2. Oracle handles the export of very large databases by splitting its export processes into background pipes into multiple filesystems. The thread that describes this, and that references the Oracle document is:

http://my1.itrc.hp.com/cm/QuestionAnswer/1,1150,0xcc4668c57f64d4118fee0090279cd0f9,00.html

Hopefully this will assist you. Good luck.

...JRF...

[Carlos Fernandez Riera]

When you want to do same backup sesions to a tape you must use norewind device /dev/rmt/xmn.

Using this device you can append files to a tape.
ie:
tar cvf /dev/rmt/0mn /tmp/1
tar cvf /dev/rmt/0mn /tmp/2
....

mt -t /dev/rmt/0mn rew # ind

tar tvf /dev/rmt/0mn

r--r--r-- xxxxxxxxxxxxxx /tmp/1

[Carlos Fernandez Riera]

When you want to do same backup sesions to a tape you must use norewind device /dev/rmt/xmn.

Using this device you can append files to a tape.
ie:
tar cvf /dev/rmt/0mn /tmp/1
tar cvf /dev/rmt/0mn /tmp/2
....

mt -t /dev/rmt/0mn rew # ind

tar tvf /dev/rmt/0mn

r--r--r-- xxxxxxxxxxxxxx /tmp/1




Use no rewind device when export directly to tape

[Carlos Fernandez Riera]

When you want to do same backup sesions to a tape you must use norewind device /dev/rmt/xmn.

Using this device you can append files to a tape.
ie:
tar cvf /dev/rmt/0mn /tmp/1
tar cvf /dev/rmt/0mn /tmp/2
....

mt -t /dev/rmt/0mn rew # ind

tar tvf /dev/rmt/0mn

r--r--r-- xxxxxxxxxxxxxx /tmp/1




Use no rewind device when export directly to tape

[John Palmer]

Hi,

fbackup will only back up disk files.

I don't know about dbexport but I assume that it will write it's export file to either a disk or tape file. If you use the non-rewind tape file then you should be OK, it's very unusual for a utility to rewind a tape before writing to it (fbackup does).

Try it! Write three dbexports to a non-rewind tape device then you can test if all three files are on tape with the mt command:-

export TAPE=/dev/rmt/?mn
mt rew
mt fsf 3

The last mt command will fail if there is only one file on the tape.

Another approach that requires spare diskspace is to 'dbexport' to a disk file then back that up to tape (non-rewind device) with dd using a large blocksize.

Regards,
John

[JGD_1]

Thanks a lot to all of you

I can now do several exports directly to the same tape (norewind device): /dev/rmt/0mn

1) mt rewind

2) dbexport dbtest1 -X -ss -t /dev/rmt/0mn -b 16 -s 24576000

3) dbexport dbtest2 -X -ss -t /dev/rmt/0mn -b 16 -s 24576000

4) dbexport dbtest3 -X -ss -t /dev/rmt/0mn -b 16 -s 24576000

If i want to import only dbtest3:

1) mt rewind
2) mt fsf 2
3) dbimport dbtest3 -t /dev/rmt/0mn -b 16 -s 24576000

The only worry i have is it i can really put 24Go on this tape ? (It's a DDS3 tape drive and i have a 24 Go tape)
where i though we could only 12 Go

JGD

[John Palmer · Accepted solution]

If that -b argument to dbexport is a blocksize then I would suggest that you increase it so that you get a blocksize of at least 64Kb. This will fit for data onto the tape and will probably be faster. It will be worth your while experimenting with various blocksizes to get the quickest run time.

The 24Gb figure assumes a 2:1 compression ratio achieved by the tape drive. You can usually better this providing that you are not writing data that has already been compressed.

I believe that the tape hardware uses a similar compression algorithm to 'gzip' so you could check how well that performs by dbexport'ing to a disk file and gzip'ing that (provided you've got the spare disk space).

Regards,
John

[Carlos Fernandez Riera]

Well 12 gb are nominal capacity of tapes ( DDS3 125m not DDS2 120m).

Using compression ( compressing 2 bytes in 1 ratio 2:1) lets you 24 GB, BUT ascii files as exports let better ratio, so dont be surprised if you can put 36 Gb in one tape.

Compresion ratio is better when data come fast to drive, and blocksize . Try different methods, dd , export ... and use big (64K) blocks.



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