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Duplicate to tape from MSDP Pool

rafanto
Level 4

‎05-28-2018 02:50 PM

Hi,

We are facing low space on 5240 appliances, for this reason, we are duplicating several historical backup images to tape.

The question is:  our MSDP is configured with enabled encryption and compression on pd.conf, what is the effect of this on tapes? because we are seeing that compression on tapes is null.

Regards

 

Rafael

0 Kudos
1 REPLY 1

mph999
Level 6
Employee Accredited

‎05-29-2018 03:06 AM

It should have no effect on tapes - once 're-hydrated' it is back to it's original form.

Firstly, what type of data is it, not everything is compressible - I suspect you have consodered this, but I'd better ask.

Next, what happens if  you take some 'non-msdp' data and just back that up to tape, does it comress or not ?

Tape hardware compression is nothing to do with NBU, if it really realy doesn't work, you have a drive issue of some sort, settings, firmware etc ...

It's possible compression on the drive is disabled:

(1)  (With compression disabled at drive level)
scsi_command -d /dev/nst1 -mode_dump

Look at page 0f, the 3rd value is 40 - this means compression is disabled on the drive.

Hex Dump of page 0x0f
0f 0e 40 80 00 00 00 ff 00 00 00 ff 00 00 00 00


(2)
You can also check using :

scsi_command -d /dev/nst1 -log_dump


***Log page (0x1b)
parameter code: 0x0000, value: 0x03f5
parameter code: 0x0001, value: 0x0000
parameter code: 0x0002, value: 0x00000000
parameter code: 0x0003, value: 0x00000400
parameter code: 0x0004, value: 0x00000000
parameter code: 0x0005, value: 0x00000065
parameter code: 0x0006, value: 0x00000000
parameter code: 0x0007, value: 0x00000000
parameter code: 0x0008, value: 0x00000000
parameter code: 0x0009, value: 0x00000000
parameter code: 0x0100, value: 0x00 <<<<<<<<<<<< Disabled

 


Now I enabled compression:

mt -f /dev/nst1 compress 1

(1)
scsi_command -d /dev/nst1 -mode_dump

Hex Dump of page 0x0f - 3rd field is now c0 = enabled
0f 0e c0 80 00 00 00 ff 00 00 00 ff 00 00 00 00

(2)
scsi_command -d /dev/nst1 -log_dump

***Log page (0x1b)
parameter code: 0x0000, value: 0x03f5
parameter code: 0x0001, value: 0x0000
parameter code: 0x0002, value: 0x00000000
parameter code: 0x0003, value: 0x00000400
parameter code: 0x0004, value: 0x00000000
parameter code: 0x0005, value: 0x00000065
parameter code: 0x0006, value: 0x00000000
parameter code: 0x0007, value: 0x00000000
parameter code: 0x0008, value: 0x00000000
parameter code: 0x0009, value: 0x00000000
parameter code: 0x0100, value: 0x01 <<<<<<<<<<<<<<<<<<<< Enabled