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BRBackup with IBM 3581 Autoloader with 2 tapes

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BRBackup with IBM 3581 Autoloader with 2 tapes

Postby jancalendar » Fri Mar 14, 2014 2:26 am

I have an IBM 3581 L17 Ultrium Autoloader with 7 slots which is used for a daily BRBackup offline backup job.
This job requires writing to 2 tape volumes.

The IBM 3581 was previously configured as Ldr REAdy.
The operator loads the 1st tape into the 1st slot of the autoloader.
The tape is picked up and sent to the read/write head.
After writing and rewinding, the tape is returned to the 1st slot.
The operator ejects this tape and loads the 2nd tape into the same slot.
After responding 'cont' to BRBackup, the job continues with the 2nd tape.

I have recently changed the IBM 3581 to SEQ REAdy.
In this case, the operator loads the 1st and 2nd tapes into slots 1 and 2 respectively.
When BRBackup completes writing, rewinding and sending the 1st tape back to slot 1, the following messages are seen:

BR208I Volume with name VVVVV02 required in device /dev/rmt1.1
BR210I Please mount the volume, if you have not already done so
BR280I Time stamp 2014-03-11 19.58.04
BR256I Please enter 'cont' to continue, 'stop' to cancel the program:

I would like to know how to set up so that the operator does not have to respond to the BR256I message above.

For your information,
backup_dev_type = tape
rewind = "tctl -f $ rewind"
rewind_offline = "tctl -f $ offline"
tape_address = /dev/rmt1.1
tape_address_rew = /dev/rmt1

Also, we DO NOT have any tape management/backup software.

The intention here is for the operators to load the 2 tapes into slots 1 and 2 and then go home after starting BRBackup.

Any help and advice would be appreciated.

Thank you.
jancalendar
 
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby hoinz » Fri Mar 14, 2014 8:38 am

I am not familiar with IBM autoloaders, but have been working with other models.
And as for your question, I think that (as it often does) the friendly manual or even the online help could be useful.
Type this on the command prompt:
brarchive -h
Pay special attention to the -c option.

hope this helps
(not sure about it though;
it has been a long time since I used it.)
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby Zavaros » Fri Mar 14, 2014 9:11 am

Hello,

it was long time since I used tapes. Sorry if I am out of sync in lot of topics.

you can use "backup_dev_type = tape_auto" to suppress the prompt to change the tape.

will the Device automatically change the tape ?

Regards,

Zav
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby jancalendar » Fri Mar 14, 2014 11:34 pm

Dear hoinz,

Thank you for your reply.

I have spent quite a bit of time going through the online documentation related to BRBackup as well as the IBM Ultrium 3581 Autoloader.

I will try out the –c option as soon as I get the chance and let you know of the results.

Thank you.
jancalendar
 
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby jancalendar » Fri Mar 14, 2014 11:40 pm

Dear Zavaros,

I have already tried
'backup_dev_type = tape_auto'.

The 1st and 2nd tapes were loaded into slots 1 & 2 respectively.

BRBackup wrote to the 1st tape and wanted to write to the 2nd tape while the 1st one was still rewinding.

(The rewinding and returning the tape to its original slot (No. 1) takes 3 to 4 minutes.)
The job therefore cancelled without loading the 2nd tape.

The console messages for the above were as follows:

BR280I Time stamp 2014-03-12 19.23.58
BR226I Rewinding tape volume in device /dev/rmt1.1 …

BR351I Restoring from /oracle/PPP/sapbackup/.tape.hdr0
BR355I from /dev/rmt1.1 …

BR241I Checking label on volume in device /dev/rmt1.1

BR280I Time stamp 2014-03-12 19.25.45
BR226I Rewinding tape volume in device /dev/rmt/1.1 …

BR208I Volume with name PPP03B required in device /dev/rmt1.1

BR280I Time stamp 2014-03-12 19.26.08
BR226I Rewinding tape volume in device /dev/rmt1.1 …
BR278E Command output of ‘LANG=C tctl –f /dev/rmt1 rewind’:
/dev/rmt1 : Device not ready
BR280I Time stamp 2014-03-12 19.26.08
BR279E Return code from ‘LANG=C tctl –f /dev/rmt1 rewind’ : 2
BR213E Winding tape volume in device /dev/rmt1.1 failed

It appears that BRBackup was ready to write to the 2nd tape whilst the IBM 3581 was not yet ready.

Do you have any suggestions how the above can be overcome?

Looking forward to your assistance.

Regards.
jancalendar
 
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby blueteeth » Sat Mar 15, 2014 1:09 pm

I read a story somewhere (or someone told me):

There was this nightly backup which spanned over two tapes. After backup of tape1, the drive would eject tape1 and wait for tape2 to be inserted for backup. All went well for some time. The administrator got lazy and asked the security guard to insert tape2 at night. The security guard was reinserting tape1 dutifully.

*An untested backup & restore is worst than having no backup*

Old dirt.
BT
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby Zavaros » Mon Mar 17, 2014 3:38 am

Hello,

Have you tried the trick described in SAP Help

Code: Select all
rewind_offline = "mt -t $ offline && sleep 240"


it will help to not return the prompt so fast.

Regards,

Zav.
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby jancalendar » Mon Mar 17, 2014 10:35 pm

Dear Zav,

I have tried the 'rewind_offline' option with sleep 60 instead of 240.

BRBackup rewound and returned the 1st tape to the 1st slot after writing.

The 2nd tape was loaded from the 2nd slot to the read/write assembly.

After rewinding and requesting the required tape volume, BRBackup proceeded to write to the 2nd tape.

(The operator was not prompted to key in <cont> for the writing to start on the 2nd tape.)

It looks like the sleep parameter has solved the ‘Device not ready’ problem.
(Thanks for your advice.)

The BRBackup however encountered a new problem after that.
The Oracle DB was mysteriously started on its own causing the BRBackup to fail.

I don't think this has anything to do with
backup_dev_type = tape_auto
rewind_offline = "tctfl -f $ offline sleep 60"
SEQ Ready.

Any ideas as to what is going on?

Regards.
jancalendar
 
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby Zavaros » Tue Mar 18, 2014 3:41 am

hello,

the primitive issue:

check the crontabs (orasid, sidadm). Do you have scheduled anything when the oracle started?

anything: brarchive, dbverify, other offline backup.
...each could startup the database only to log their returncode to the database..

Advanced issue:
- you still could have timing issues ... somewhere.

Regards,
Zav
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby jancalendar » Wed Mar 19, 2014 10:57 pm

Dear Zavaros,

Thank you for your response.

We checked and found that the Oracle DB was started accidentally as a result of an operator error.

We monitored the backup over the last 2 nights and found that the backup completed without any errors.

On checking the BRBackup log, we found that the total time taken for the backup was in fact longer than when the operator had to eject the 1st tape, load the 2nd tape and then reply <cont>. (i.e. the previous setup).

In the InitPPP.sap parameter, we currently specify

compress = no
tape_size = 90000M

The 3581 L17 Autoloader supports hardware compression. DC (Data Compression) is shown on the LED panel during the backup.

The amount of data processed by BRBackup was 143506MB.

We are using 100GB/200GB LTO tapes.

We would like to have BRBackup complete in a shorter time.

Q1: Is it possible to use hardware compression and complete the backup on one (1) tape ?

Q2: What parameters do you suggest to achieve this?

I looked at SAP Note 8707 which did not gave any clear answers.

Thank you.
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby Zavaros » Thu Mar 20, 2014 7:25 am

Hello,

tape backups are dumb. SAP knows that the tape capacity is 90GB so it pushes 90GB to a single tape. If compression is set (yes or hardware) then SAP divides the tape capacity by the compression rate (I do not remember the right formula) ... an pushed that amount of data to the tape.

so in case of 50% compression rate SAP will send 180GB data to the 90GB tape.

Therefore, you can try:
- increase the tape capacity from 90GB to 160GB
- set "compress = hardware". In this case SAP needs to know the compression rate of the database. Therefore you have to run a compression tests before the backup.

the result in both cases will be same: SAP sends more data to a single tape. The difference is that in first case you enforce a fix compression rate while in 2nd case SAP calculates something dynamically.

the speed can be affected by several factors. Can you pinpoint where was the delay?
Which tool do you use to send data to tape? cpio or dd? what are the parameters? same parameters were used before?

Regards
Zav

PS: hardware compression is optimized on speed its compression rate is as bad as the compress command in unix. I suggest to make tests with software compression using gzip.
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby jancalendar » Thu Mar 20, 2014 10:02 pm

I
Dear Zavaros,

Thank you for your response.

1. Longer Backup Time

In answer to your queries, the settings and recent changes are as follows:

A .BRBackup parameters:

‘dd’ is used to send data to tape.

The only parameters that were changed were:

Backup_dev_type : from "tape" to "tape_auto"

Rewind_offline : from “tctl –f $ offline” to “tctl –f $ offline && sleep 60”


B. At the hardware level, the IBM 3581 L17 was changed from Ldr Ready to SEQ Ready.

I am still not able to pin-point the cause of the delay.

I was expecting a faster completion time as the 60 seconds sleep defined in the rewind_offline is
shorter than the time taken for the operator to manually eject the 1st tape, load the 2nd tape and respond <cont> when the 2nd tape is ready.

I read somewhere that SAP ‘optimizes’ the usage of the declared media and in my case, split the files to be backed up onto the 2 tape volumes as
equally as possible.

Q. Do you think this is true?


2.Faster Backup Job Completion

I would first like to try with

“compress = no” and “tape_size = 160G”

Q2. Will the IBM 3581 L17 Tape Drive take the data dumped by BRBackup and compress it on its own?

Depending on the outcome of the above, we will try with “compress = hardware” as well as
look into using gzip as you suggested.

Thank you.
jancalendar
 
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby Zavaros » Fri Mar 21, 2014 6:29 am

Hello,

if the compression led lights/blinks on the device then the it uses compression. It can be turned off only with special commands.
In the init.sap the difference between compress=hardware and no is that SAP calculates with compression rate or not.

what are the parameters of "dd"? there should be something like "bs=..." or "obs=...".
the BlockSize could affect the backup time significantly.

Regards,
Zav
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby jancalendar » Mon Mar 24, 2014 5:02 am

Dear Zav,

The DC (Data Compression) LED on the IBM 3581 is ON but does not Blink.

The DD parameters are as follows:

dd_flags = "obs=64k bs=64k"
dd_in_flags = "ibs=64k bs=64k"

They were not changed from the time when we used "backup_device =tape".

Regards.
jancalendar
 
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Re: BRBackup with IBM 3581 Autoloader with 2 tapes

Postby Zavaros » Tue Mar 25, 2014 7:36 am

Hi,

if the block size was not changed then the speed issue is somewhere else.

the parameters could be increase it to 256k. It will increase the write speed but it decreases tolerance to tape errors because a bigger block has to be written again in case of media error.

Regards,
Zav
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