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frecover help

 
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Paul_481
Respected Contributor

frecover help

Hi,

I use fbackup to save our database. The total size of the file is 150 Gb and 17 filesytem. I am using DDS4 and the backup consume 7 tapes.

Now I want to restore a particular filesystem, about 80 Gb, After reading the first tape it ask for the second tape, but when I insert it it said that its not the second tape.

Are there any special procedure on restoring from multiple tapes? Is there an easy way to restore this?

Thanks and Regards,

Paul
11 REPLIES 11
Paul_481
Respected Contributor

Re: frecover help

I got this message:

#frecover -f /dev/rmt/0m -i /data15/oradata/MINOP -xv
frecover(5401): Volume 1 completed.
frecover(5404): Press return when the next volume is ready on /dev/rmt/0m:

I INSERT THE 2ND TAPE

frecover(5423): incorrect volume mounted;
frecover(5424): expected volume 2, and got 1
frecover(5433): Do you wish to continue using this volume? (^[yY]/^[nN]) n
frecover(5412): Do you wish to try to salvage this volume? (^[yY]/^[nN]) n
frecover(5411): Do you wish to try a different volume? (^[yY]/^[nN]) y
frecover(5404): Press return when the next volume is ready on /dev/rmt/0m:

I INSERT THE 3RD TAPE

frecover(2105): did not find expected file marker
frecover(5409): unable to read volume header
frecover(5418): not an fbackup volume; unable to read volume header
frecover(2105): did not find expected file marker
frecover(5412): Do you wish to try to salvage this volume? (^[yY]/^[nN]) n
frecover(5411): Do you wish to try a different volume? (^[yY]/^[nN]) y
frecover(5404): Press return when the next volume is ready on /dev/rmt/0m:

Any solution?

Thanks,

Paul
john korterman
Honored Contributor

Re: frecover help

Hi,

fbackup starts by writing an index file of the files to include in the backup on the first tape. At the time this is being done, fbackup does not know how many tapes are required for holding the files. I think that the message concerning the next tape just indicates that the file was not found on the first tape. There is hardly any other option than trying to insert the tapes - one by one - until fbackup finds the location of the data. Alternatively, you could perhaps have guessed the correct tape, if you had recorded which files were stored on each tape when the backup was made.
I hope that is how it works, good luck.

regards,
John K.
it would be nice if you always got a second chance
Paul_481
Respected Contributor

Re: frecover help

Okay, so that means I can go directly to tape 7 if I know that the specific file is in there? Is there a need for the frecover to read all tapes one by one?

Regards,

Paul
john korterman
Honored Contributor

Re: frecover help

Hi again,
I think you always have to start with tape no. 1 (even though the index should be on all tapes used) and then you could insert no. 7 when it asks for the next tape, if you know for sure that this tape will hold the requested data. However, I must admit that I am not sure. Perhaps other members know.

regards,
John K.
it would be nice if you always got a second chance
Bill Hassell
Honored Contributor
Solution

Re: frecover help

Here is the procedure for all fbackup multi-tape sets: Always put the *LAST* tape in first. Here's the reason: fbackup has no way to tell how much data will fit on each tape. Compression and bad spots on the tapes make this impossible to predict. Once fbackup reaches the end of the first tape, it requests the next tape. The first thing written on each tape is the fbackup header (which includes the tape number) plus a complete index of all files and directories that will be saved and a marker as to the first file on this new tape.

So tape #2 knows exactly what's on tape #1, tape #3 knows about tape #1 and #2, and so on. Only tape #7 knows where all files are located. Since the index can be read in just a few seconds, you can reach any file or directory in just a few minutes with just two tape changes. This technique is very common with commercial backup programs. Note that high speed search is standard with fbackup/frecover but is disabled when the destination is not a 'real' DDS or DLT tape (ie, a network connection)

However, these two messages indicate a very serious situation:

> I INSERT THE 2ND TAPE

> frecover(5423): incorrect volume mounted;
> frecover(5424): expected volume 2, and got 1

This means that what you thought was tape #2 is the original tape.

> I INSERT THE 3RD TAPE

> frecover(2105): did not find expected file marker
> frecover(5409): unable to read volume header
> frecover(5418): not an fbackup volume; unable to read volume header

This means that the 3rd tape has nothing to do with fbackup. It is a tar or cpio tape or somehow got overwritten or mixed up in your backup set. Based on this and the previous tape, you don't have a useful backup of your data at all! This illustrates the difficulties in managing multi-tape backups. Very careful marking and handling of the tapes is critical. fbackup will record a volume header on each tape. Use:

frecover -V - -f /dev/rmt/

on each tape to read the header. If you are not using a config file with your fbackup command (-c option), your tapes are not being recorded efficiently at all and you may be able to reduce the recording time for each tape by 30-60%, perhaps reducing the tape count from 7 to only 4-6 tapes. Put this into a file in /etc/fbackup.conf:

blocksperrecord 512
records 64
checkpointfreq 1024
readerprocesses 6
maxretries 5
retrylimit 5000000
maxvoluses 200
filesperfsm 2000

Then run fbackup with the required options plus: -c /etc/fbackup.conf

The reason that this helps is that the defaults are designed for reel-to-reel tape drives, not DDS or DLT/LTO.


Bill Hassell, sysadmin
Bill Hassell
Honored Contributor

Re: frecover help

One additional suggestion: to avoid tape handling errors like this, I would get a DDS changer. That way, all the tapes stay together in a removeable holder. Also, make sure that no one has read or write access to the tape device files! All the files in /dev/rmt should be 600 permissions (never 666 or 777). You don't experimenters trying to write or read your backup tapes.


Bill Hassell, sysadmin
Paul_481
Respected Contributor

Re: frecover help

Guys,

I really appreciate all your help. Thanks everyone for the reply.

I'll try your suggestions.

Regards,

Paul
Paul_481
Respected Contributor

Re: frecover help

Hi,

I tried to use the last tape (tape 7)first for frecover but it ask for tape 1.

Any comments?

Regards,

Paul
Paul_481
Respected Contributor

Re: frecover help

Is there any special procedures when using the last tape first?
Bill Hassell
Honored Contributor

Re: frecover help

No special procedure. Tape #7 knows that the file/directory you need is on tape #1. Make sure that the volume header for tape number 7 matches tape #1. It's possible that tape #1 has a portion of the directory you need and the rest is on tape #2 and possibly #3. But based on the message above, tape #2 is marked as tape #1 (probably from some other backup). That's why you need to compare the -V output from frecover on each tape. Look for these 3 fields:

Time:Mon Jan 10 08:07:21 2005
Volume Number:1
Backup Identification Tag:25068 1105362441

These will tell you if the #2 tape belongs with the #1 and #7 tapes.


Bill Hassell, sysadmin
Paul_481
Respected Contributor

Re: frecover help

Thanks Again