[SunHELP] query on "tape" operation

[Paul Walsh]

Make sure you are using the correct length tape for your drive (and the
correct density letter) 

>From InfoDoc 16501:
 

Infodoc ID   Synopsis   Date 
16501   4mm tape drive matrix   19 Jan 2001 

Description Top 

                         4mm Tape Drives

TYPE          MAXIMUM TAPE     NATIVE         ADVERTISED CAPACITY
              LENGTH (meters)  CAPACITY (Gb)  W/COMPRESSION (Gb)
------------------------------------------------------------------
Single drives:                   

DDS-1             60           1.3 [l]           2.6 [m]

DDS-DC            90           2   [l]           5   [m]

DDS-2            120           4   [l]           8   [m]

DDS-3            125          12   [l]          24   [m]

-------------------------------------------------------------------
Autoloaders:

DDS-DC            90           8   [l]          16   [m]
(4 tape magazine)

DDS-2            120          16   [l]          32   [m]
(4 tape magazine)

DDS-3            125          72   [l]         144   [m]
(6 tape magazine)
-------------------------------------------------------------------

Notes:

1. Letters in square brackets above are suggested density flags.

2. /dev/rmt density specifiers:  typically "l" (low) is used for native
mode,
   and "m" (medium) is used to turn on the compression feature on the
drives.
   Most density specifiers other than "l" will perform compression, but "m"
   seems to be the convention at Sun.

3. Marketing usually advertises tape drive capacity by assuming a 2:1
   compression ratio.  In reality, the resulting capacity is generally
   about 1.8:1 .  So for a drive that holds 4Gb in native mode, like the
   DDS-2, the capacity derived using hardware compression is usually 7Gb.
   Note that the DDS-DC model was advertised assuming a 2.5:1 ratio instead
   of the traditional 2:1 ratio.

4. Media is NOT backwards compatible.  For example, DO NOT use a 120m tape
   in an DDS-DC.  However, you CAN use a 60m tape in an DDS-2.

5. Identifying the drives:  If you don't see any markings on the front of
the
   unit it is most likely a DDS-1 or a DDS-DC.  Otherwise, the drive will be
   identified on the faceplate.


Hope that helps

Paul Walsh

Senior Systems Administrator, IT Services,
University of Central England, BIRMINGHAM B42 2SU, UK
Tel: +44 (0)121 331 5708	Fax: +44 (0)121 356 2875


 

-----Original Message-----
From: TAG DBA [mailto:dbatag at tatainfotech.com]
Sent: 14 December 2001 11:17
To: 'sunhelp at sunhelp.org'
Subject: [SunHELP] query on "tape" operation


Solaris 8 on Sun E450
----------------------------------
I was trying to estimate how many sets of database backups can fit onto one
4 GB DAT tape.
One set approx is of size 1 GB. So atleast 3 sets should get copied to tape.
The command I type is :
$ tar cvf /dev/rmt/0cn $DUMPS

However during the third copy operation I got this error:

a ./archlogs_14_dec_01.Z 696322 tape blocks
tar: write error: unexpected EOF
Backing up export dump expTAG1SPZ_Fri_full.dmp.Z and log file
/s0003/TAG1SPZ/expdumps/expbu_TAG1SPZ_14_dec_01.log ....
a expTAG1SPZ_Fri_full.dmp.Z 563396 tape blocks
tar: write error: unexpected EOF
Ending Backup Fri Dec 14 16:54:19 GMT 2001

Does it mean that the tape is full ???
Regards,
~aslam
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