Re: [Mtx-general] AIT-3 Tape full with 42G

[Kevin W. <kj...@ri...>]

 From Charles M. Richmond
> Another question that maybe this list can help me with. The SDX2-50C
> tapes claim to hold 50G uncompressed and 100G compressed but I am
> unable to fit more than 42G and compression does not seem to make 
> a difference. The configuration is Solaris 8 on an E250 with an
> Overland LibraryPro changer with 2 SDX-700C AIT-3 drives. The version
> of mtx is 1.2.18rel and 'ufsdump' is used to write the tape. This
> is only marginally on topic but I am hoping that someone spots
> something in the (mtx) tapeinfo command output that is incorrect
> or that folks just tell me that the 50G/100G is marketing nonsense.

well, the 50G is likely a "marketing" gigabyte, namely 50*10^9.
If you convert to 50*2^30, the difference is ~8%, but converting
marketing to a power of two results in 50*10^9 / 2^30 = 46.5

also, I don't know if the size reported by ufs dump is before or after
blocking for tape.  Like tar, dump breaks up the data into blocks and
writes said blocks out to tape. this naturally increases the overhead.

If you want to really know how many bytes you can put on tape, I recommend
using dd. something like

	/bin/yes | dd of=/dev/rmt/0c bs=1000

'yes' will provide you with an infinite string of 'y<enter>', and the dd
will write out in chunks of 1000 bytes, but with no overhead.  at the end,
the tape will fill up and tell you how many blocks it wrote out.  Multiply
by 1000, and you can tell how many bytes were written out.

Also, since 'y<enter>' is highly compressible, it will tell you if
compression is working properly.  the tape driver may not be signaling
the drive correctly for compression mode.  Suggest you check for patches
to the tape driver and specific support for your drive.

   - Kevin

> Below I have appended the results of a tapeinfo and a ufsdump:
> 
> 
> # tapeinfo /dev/rmt/0c
> argc=2Usage: tapeinfo -f <generic-device>
> # tapeinfo -f /dev/rmt/0c
> Product Type: Tape Drive
> Vendor ID: 'SONY    '
> Product ID: 'SDX-700C        '
> Revision: '0101'
> Attached Changer: No
> SerialNumber: '0006885030'
> MinBlock:2
> MaxBlock:16777215
> Ready: yes
> BufferedMode: yes
> Medium Type: Not Loaded
> Density Code: 0x31
> BlockSize: 512
> DataCompEnabled: yes
> DataCompCapable: yes
> DataDeCompEnabled: yes
> CompType: 0x3
> DeCompType: 0x3
> BOP: yes
> Block Position: 0
> # 
> # tapeinfo /dev/rmt/0c
> argc=2Usage: tapeinfo -f <generic-device>
> # tapeinfo -f /dev/rmt/0c
> Product Type: Tape Drive
> Vendor ID: 'SONY    '
> Product ID: 'SDX-700C        '
> Revision: '0101'
> Attached Changer: No
> SerialNumber: '0006885030'
> MinBlock:2
> MaxBlock:16777215
> Ready: yes
> BufferedMode: yes
> Medium Type: Not Loaded
> Density Code: 0x31
> BlockSize: 512
> DataCompEnabled: yes
> DataCompCapable: yes
> DataDeCompEnabled: yes
> CompType: 0x3
> DeCompType: 0x3
> BOP: yes
> Block Position: 0
> # 
> 
> 
>   DUMP: Writing 32 Kilobyte records
>   DUMP: Date of this level 0 dump: Thu Jul 24 13:09:54 2003
>   DUMP: Date of last level 0 dump: the epoch
>   DUMP: Dumping /dev/rdsk/c1t1d0s0 (tub.ma.intuit.com:/dumps) to /dev/rmt/0c.
>   DUMP: Mapping (Pass I) [regular files]
>   DUMP: Mapping (Pass II) [directories]
>   DUMP: Estimated 96007110 blocks (46878.47MB).
>   DUMP: Dumping (Pass III) [directories]
>   DUMP: Dumping (Pass IV) [regular files]
>   DUMP: 12.50% done, finished in 1:10
>   DUMP: 25.27% done, finished in 0:59
>   DUMP: 37.79% done, finished in 0:49
>   DUMP: 50.24% done, finished in 0:39
>   DUMP: 63.08% done, finished in 0:29
>   DUMP: 75.54% done, finished in 0:19
>   DUMP: 87.93% done, finished in 0:09
>   DUMP: End-of-tape detected
>   DUMP: Tape rewinding
>   DUMP: 97.45% done, finished in 0:02
>   DUMP: Change Volumes: Mount volume `#2' on `tub.ma.intuit.com:/dev/rmt/0c'
>   DUMP: NEEDS ATTENTION: Is the new volume (#2) mounted on `tub.ma.intuit.com:/d
> ev/rmt/0c' and ready to go?: ("yes" or "no")   DUMP: The ENTIRE dump is aborted.