How can I set data compression in Solaris 9?

Posted on 2003-03-28
Medium Priority
Last Modified: 2013-12-27
We have a SunFire V480 server running Solaris 9 (36GB HD) that has a external HP SureStore DAT tape drive attached.  The tape drive is DDS4; native 20GB capacity with 40GB compressed. We have exceeded the 20GB capacity.  

How can I set the data compression so I will be able to use all of the tape drive capacity?
I was told to change "/dev/rmt/1n" (1n is what we use now) to "/dev/rmt/1un" (ultra) but that did not work.  

Your help will be greatly appreciated!
Question by:dee43
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions

Accepted Solution

soupdragon earned 1000 total points
ID: 8224052
Didn't work or didn't give you any compression? What backup utility are you using?

As I understand it the un (ultra compressed) and cn (compressed) devices are identical but try with /dev/rmt/1cbn just in case.

Check that your tape device is featured in the tape device config file /kernel/drv/st.conf. If the device is being picked up correctly then device type should show up in the /var/adm/messages file - and indeed if you call 'mt -f /dev/rmt/1cn status'.

Finally is there a significant amount of compressed data on the drive you are backing up (.Z, .zip etc. files)? If the data on disk is largely compressed (database_dumps.Z etc) then you won't get an awful lot of compression on the tape.



Expert Comment

ID: 8224115

n = not rewint

c = compression
LVL 38

Expert Comment

ID: 8224318
if you tape driver support compress (hardware compress) than you can use /dev/rmt/1nc as the above comments.

if you don't have a tape device with that capability you can, use "usfdump + compress + dd" to do the backup :


ufsdump 0f - /fs | compress | dd of=/dev/rmt/1n obs=20480

And the corresponding rstores would look like:
dd if=/dev/rmt/1n | compress -d | ufsrestore -

use GNU tar with -z (compess option) to do the job, you can download GUN tar from:
use GNU tar:
If you used Gnu tar to back up whatever in mydir the with something like:

cd /path-to/mydir
tar cvzf /dev/rmt/1n .

then you would restore the data with:

cd /path-to/mydir
tar xvzpf /dev/rmt/1n

Get 15 Days FREE Full-Featured Trial

Benefit from a mission critical IT monitoring with Monitis Premium or get it FREE for your entry level monitoring needs.
-Over 200,000 users
-More than 300,000 websites monitored
-Used in 197 countries
-Recommended by 98% of users


Expert Comment

ID: 8224894
The /dev/rmt/1cbn device should do the job, but if you require any compressed files to be made smaller, I'd suggest getting a copy of gzip from www.sunfreeware.com and using that to compress your files. HTH.

Author Comment

ID: 8226061

dev/rmt/1cbn worked!  BTW, we are using ufsdump to do our backups. What does the "b" stand for and will I have to decompress files when I do a restore (ufsrestore)?


Expert Comment

ID: 8226927
b stands for Berkeley-style device, leaving it off reverts to At&T-style as explained here:

When a file open for reading only is closed and the no-rewind bit is not set, the tape is rewound.  If the no-rewind bit is set, the behavior depends on the style mode.  For AT&T-style devices, the tape is positioned after the EOF following the data just read.  For Berkeley-style devices, the tape is not repositioned in any way.

You can leave the b off and it should still work. Some backup systems, like Legato, require the b option since they use record rather than file level repositioning.

Under normal circumstances the two modes seem pretty interchangable unless the application specifies otherwise.


Featured Post

Optimize your web performance

What's in the eBook?
- Full list of reasons for poor performance
- Ultimate measures to speed things up
- Primary web monitoring types
- KPIs you should be monitoring in order to increase your ROI

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction Regular patching is part of a system administrator's tasks. However, many patches require that the system be in single-user mode before they can be installed. A cluster patch in particular can take quite a while to apply if the machine…
Every server (virtual or physical) needs a console: and the console can be provided through hardware directly connected, software for remote connections, local connections, through a KVM, etc. This document explains the different types of consol…
Learn how to get help with Linux/Unix bash shell commands. Use help to read help documents for built in bash shell commands.: Use man to interface with the online reference manuals for shell commands.: Use man to search man pages for unknown command…
Learn how to navigate the file tree with the shell. Use pwd to print the current working directory: Use ls to list a directory's contents: Use cd to change to a new directory: Use wildcards instead of typing out long directory names: Use ../ to move…
Suggested Courses
Course of the Month14 days, 18 hours left to enroll

771 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question