Solaris 11 - What Are Tape Drive /dev/rmt/ dcbn Devices ? - DADP Digital Archive Data Protection

Asset ID:	1-71-2023369.1
Update Date:	2018-03-07
Keywords:

Solution Type Technical Instruction Sure

Solution 2023369.1 : Solaris 11 - What Are Tape Drive /dev/rmt/ dcbn Devices ? - DADP Digital Archive Data Protection - How to Disable DIV

Applies to:

Sun SPARC Enterprise M4000 Server - Version Not Applicable and later
Solaris Operating System - Version 11 and later
Information in this document applies to any platform.

Goal

Starting Solaris 11 you can find new tape devices on /dev/rmt with the letter d after the st device number

See this example for tape drive that corresponds to st instance 0

# ls -l /dev/rmt/0*
lrwxrwxrwx   1 root     root          82 May 5 09:55 0 -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:
lrwxrwxrwx   1 root     root          83 May 5 09:55 0b -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:b
lrwxrwxrwx   1 root     root          84 May 5 09:55 0bn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:bn
lrwxrwxrwx   1 root     root          83 May 5 09:55 0c -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:c
lrwxrwxrwx   1 root     root          84 May 5 09:55 0cb -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:cb
lrwxrwxrwx   1 root     root          85 May 5 09:55 0cbn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:cbn
lrwxrwxrwx   1 root     root          84 May 5 09:55 0cn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:cn
lrwxrwxrwx   1 root     root          83 May 5 09:55 0d -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:d
lrwxrwxrwx   1 root     root          84 May 5 09:55 0db -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:db
lrwxrwxrwx   1 root     root          85 May 5 09:55 0dbn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dbn
lrwxrwxrwx   1 root     root          84 May 5 09:55 0dc -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dc
lrwxrwxrwx   1 root     root          85 May 5 09:55 0dcb -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dcb
lrwxrwxrwx   1 root     root          86 May 5 09:55 0dcbn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dcbn
lrwxrwxrwx   1 root     root          85 May 5 09:55 0dcn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dcn
lrwxrwxrwx   1 root     root          84 May 5 09:55 0dh -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dh
lrwxrwxrwx   1 root     root          85 May 5 09:55 0dhb -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dhb
lrwxrwxrwx   1 root     root          86 May 5 09:55 0dhbn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dhbn
lrwxrwxrwx   1 root     root          85 May 5 09:55 0dhn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dhn
lrwxrwxrwx   1 root     root          84 May 5 09:55 0dl -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dl
lrwxrwxrwx   1 root     root          85 May 5 09:55 0dlb -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dlb
lrwxrwxrwx   1 root     root          86 May 5 09:55 0dlbn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dlbn
lrwxrwxrwx   1 root     root          85 May 5 09:55 0dln -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dln
lrwxrwxrwx   1 root     root          84 May 5 09:55 0dm -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dm
lrwxrwxrwx   1 root     root          85 May 5 09:55 0dmb -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dmb
lrwxrwxrwx   1 root     root          86 May 5 09:55 0dmbn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dmbn
lrwxrwxrwx   1 root     root          85 May 5 09:55 0dmn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dmn
lrwxrwxrwx   1 root     root          84 May 5 09:55 0dn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dn
lrwxrwxrwx   1 root     root          84 May 5 09:55 0du -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:du
lrwxrwxrwx   1 root     root          85 May 5 09:55 0dub -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dub
lrwxrwxrwx   1 root     root          86 May 5 09:55 0dubn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dubn
lrwxrwxrwx   1 root     root          85 May 5 09:55 0dun -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:dun
lrwxrwxrwx   1 root     root          83 May 5 09:55 0h -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:h
lrwxrwxrwx   1 root     root          84 May 5 09:55 0hb -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:hb
lrwxrwxrwx   1 root     root          85 May 5 09:55 0hbn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:hbn
lrwxrwxrwx   1 root     root          84 May 5 09:55 0hn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:hn
lrwxrwxrwx   1 root     root          83 May 5 09:55 0l -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:l
lrwxrwxrwx   1 root     root          84 May 5 09:55 0lb -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:lb
lrwxrwxrwx   1 root     root          85 May 5 09:55 0lbn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:lbn
lrwxrwxrwx   1 root     root          84 May 5 09:55 0ln -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:ln
lrwxrwxrwx   1 root     root          83 May 5 09:55 0m -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:m
lrwxrwxrwx   1 root     root          84 May 5 09:55 0mb -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:mb
lrwxrwxrwx   1 root     root          85 May 5 09:55 0mbn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:mbn
lrwxrwxrwx   1 root     root          84 May 5 09:55 0mn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:mn
lrwxrwxrwx   1 root     root          83 May 5 09:55 0n -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:n
lrwxrwxrwx   1 root     root          83 May 5 09:55 0u -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:u
lrwxrwxrwx   1 root     root          84 May 5 09:55 0ub -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:ub
lrwxrwxrwx   1 root     root          85 May 5 09:55 0ubn -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:ubn
lrwxrwxrwx   1 root     root          84 May 5 09:55 0un -> ../../devices/pci@0,600000/pci@0/pci@9/SUNW,emlxs@0/fp@0,0/st@w25000021884xxxxx,1:un

# ls -l /dev/rmt/0* |wc -l
      48

Solution

1. There is a new feature "DADP Digital Archive Data Protection " implemented on st driver starting with Solaris 11

This is also known as DIV (Date Integrity Validation)

From man st :

Data Protection
     Drives that support SCSI T10 standard Logical Block Protec-
     tion has a minor node that have the letter d after the dev-
     ice number. If these nodes are opened this enables this pro-
     tection. This sets the drive to check per block CRCs that
     are added to each block as they are writen and again when
     those blocks are read back. The host also checks and compare
     the CRCs before returning them to the reading application to
     insure there has been no data curruption.

....

     Devices that support Data Protection requires a conf file
     entry to configure this feature. After the st_dadp_settings=
     entry is a list of drives and their configurations. Each
     list member has the Vendor and Product in double quotes, a
     comma, then an CRC algorithm name in double quotes, a comma,
     a configuration name to be associated with that type of
     drive, which is also double quoted. Each entry is delimited
     from the next entry by a comma, and the last entry is ter-
     minated with a semicolon.

     The currently supported CRC algorithms are sb-2, crc32c, and
     reed-solomom.

     If you wish to explicitly disable data protection for type
     of drive you can use the name DISABLED to prevent Data pro-
     tection.

     If a match is found between an entry in the st_dadp_settings
     and the Inquiry information returned from a drive being con-
     figured, it looks for and used the configuration name speci-
     fied.

     Each named configuration has a unique name followed by an
     equal sign and four values.

     <method>      The values that are mode selected to the drive
                   to put it into Data Protection mode. This
                   entry is followed by a comma.

     <crc-size>    The number of bytes required to contain the
                   CRC. This entry is followed by a comma.

     <data_mod>    If the drive requires data to be evenly
                   divisible by specific value, usually the power
                   of 2, that power of 2 is used here. If data
                   size must be evenly divisible by 4, you would
                   use 2, since 2 to the second power is 4. This
                   entry is followed by a comma.

     <crc_seed>    The initial value used to start the CRC calcu-
                   lation.

     Each named configuration is completed with a semicolon.

2. See these other documens with examples about this feature:
SAM-QFS: Stager Fails Reading T10000D (T10kD) With DIV Turned On (Doc ID 1622062.1)
T10000D - DIV Problem With SAM QFS And Solaris Configuration (Doc ID 1621436.1)

3. How to disable DADP feature?

If you don't want to use this feature, remove device files with the 'd' on /dev/rmt
To make changes permanent, you need to disable the DADP feature for that particular tape drive model

As an example, if your tape drive is an LTO IBM ULTRIUM-TD5 :

Add the following line to the st_dadp_settings value in file /etc/driver/drv/st.conf
st_dadp_settings = "IBM ULTRIUM-TD5", "DISABLED", "";
(notice there are 5 spaces between IBM and ULTRIUM)

Then reboot the server.

After reboot no /dev/rmt/Xd* entries exists anymore for these tape drives. The device files with the 'd' are not created.

About disable DADP , see also:
Bug 19661830 : Improve st error handling with tape device having no DADP support

References

<NOTE:1621436.1> - T10000D - DIV Problem With SAM QFS And Solaris Configuration
<BUG:19661830> - IMPROVE ST ERROR HANDLING WITH TAPE DEVICE HAVING NO DADP SUPPORT
<NOTE:1622062.1> - SAM-QFS: Stager Fails Reading T10000D (T10kD) With DIV Turned On

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