SUMMARY - Filesystem Compression

From: Andy J. Stefancik 206-237-2164 (
Date: Mon Jun 13 1994 - 08:49:37 CDT

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> I am looking for a file compression utility at the filesystem level,
> ideally with the capability to only compress/uncompress tagged files.
The Magma Crusher was the most widely recommended. I passed this info on
to the organization in need. It doesn't do file tagging though. Some others

There are a couple of such things on the market. DotZ and PowerOpen (I
think that's the name) come to mind. Check the back of a Unix trade
rag for ads. has such a product I believe.

I saw a product called PowerDrive about 1 year ago, but I've not used it
and I'm not sure if the company is still in business. I'm attaching the
ad from SunFlash.

I'm including details of Magma Crusher and PowerDrive

Andy Stefancik Internet:
Boeing Commercial Airplane G. UUCP: ...!uunet!bcstec!eerpf001!as6143
P.O. Box 3707 MS 64-25 Phone: (206) 237-2164
Seattle, WA 98124-2207
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knowing more details, our Crusher product should work for you. Following are
some details. Let me know if you'd like an eval copy. Crusher is priced at $

Best Regards,

Bob Fries

             "Crusher" File System can Double your Disk Space!

      CRUSHER is a SunOS file system that transparently compresses and
decompresses data on a workstation's disk drive thereby saving enormous
amounts of disk space. CRUSHER typically delivers a 2:1 compression
ratio. All file types are supported: directories, executables, plain
files, links, sockets, mapped files, and files from custom applications
all can be compressed by CRUSHER. All system administration tools,
programming languages, office productivity applications and CAD programs
will operate in concert with CRUSHER as will Open Windows, Motif, X
Windows and other GUIs.

      The transparent nature of the compressed file system provides
seamless integration into Open Systems environments and allows NFS
access to all compressed files.

      CRUSHER operates by providing the user with the capability to
create compressed partitions on any disk drive. All data read or
written to the compressed partition will be compressed and decompressed
automatically, on the fly as it is needed. CRUSHER uses the same
lossless algorithms used in tape backup units and will not corrupt or
lose data.

      CRUSHER will work with any disk drive. It has passed rigorous
testing on a wide variety of models from all leading disk drive
manufacturers. CRUSHER performed flawlessly on all drives tested with
significant increases in capacity.

      Installation is simple, an automatic installation script is
provided. No kernel reconfiguration or recompiling of programs is

                      Frequently Asked Questions

How do I evaluate CRUSHER?

CRUSHER is a file system, and as such, operates on partitions. So,
select a partition that you want to compress, backup the data, unmount
the partition, run newcfs, remount it as a compressed file system and
restore the data to the partition. You can the use df command to show
you the available space on the partition. Run some applications that
use data located on the partition. We believe that you will see no
noticeable difference in the speed of your application, but try it

How is the compression/decompression done?

CRUSHER, as we said above, is a file system and operates on partitions.
In other words, space is set aside on your disk for various uses such as
swap space, the root partition, operating system executables, etc. and these
various spaces are called partitions. Partitions are "mounted" using the
mount command or mount automatically at boot through the file called fstab.
When the partition is mounted, a file system (in our case, the CRUSHER
file system "cfs") is specified and, from then on, all reads and writes to
that partition use the CRUSHER file system

The CRUSHER file system code operates on pages of data. It compresses
each page it writes before the data is sent to the disk driver. When
data is read, the CRUSHER file system code decompresses only the data
representing the particular page that the data resides in. The entire
file is not decompressed at once, data is only decompressed as needed
when needed.

How does the performance of CRUSHER compare with the standard file

On a per page basis, CRUSHER takes twice as long to read and decompress
the data as the standard file system. Subjectively, you will not notice
any difference in performance of your favorite application unless it is
extremely disk I/O intensive.

CRUSHER compresses and decompresses the data in files and that requires
CPU time. CRUSHER takes approximately 20% longer to compress and write
files to the disk then the standard file system. Compression is typically
done once, when the file is created or restored from backup. When a file
is modified, only the pages that are actually modified are rewritten. The
whole file is NOT recompressed.

When data is decompressed, only the page that the data resides in is

The reason you do not notice any speed differences in a typical
environment is because Solaris uses buffer cache to speed read/write
operations. When data is written, it is written uncompressed into the
buffer cache. This data can be read without accessing the disk at
memory speeds. Only when the data is flushed from the cache (update
flushes the cache every 30 seconds) is the data compressed. When you
read, a full page of data is read and decompressed into the buffer cache
and all data accesses are done directly from the buffer cache.

What versions of the OS does it work with?

CRUSHER is currently available for SunOS 4.1.x. Solaris 2.x and X86
will soon be supported also.

What computers does it work with?

CRUSHER works with all Sun Microsystems SPARC computers and SPARC clones
running SunOS 4.1.x.

Can files compressed with CRUSHER be accessed remotely through NFS?

Yes, compressed file systems can be exported. Only the server needs
to have CRUSHER installed and licensed.

What kind of compression ratios can I expect?

The amount of compression will depend on the redundancy in your data,
however, we have tested several types of files and have seen the
following ratios:

          Type of File Compression ratio

        SPARC executables 1.7:1
        man pages (ASCII) 4.3:1
           AnswerBook 2.1:1
         ASCII database 2.6:1
          /usr/openwin 2.1:1
          AutoCAD Model 2.5:1

How do I install CRUSHER?

Installation is very simple, it consists of "tar"ing the floppy and
running an installation script. You will also have to back up your
data if it already exists, decide which partitions to make into
compressed file systems, modify /etc/fstab to automatically mount the
compressed file systems, and then restore your data to the compressed
file systems.

How does the licensing work?

CRUSHER is shipped with a 30 day license that is automatically installed
by the installation script. Within 30 days after installation, you need
to call us and get a permanent license that is good for your computer.
The license is hostid locked and only good for one computer.

If you do not get your license, CRUSHER will, after 30 days, stop
compressing and eventually will start slowing down and will continue to
slow down until it becomes almost unusable. So, please call for your license.

What if I want to return it?

We hope CRUSHER works for you, but, if for any reason you want to return
the product you may do so before you get your permanent license. Please
call first to arrange the return. No returns will be accepted after you
receive your permanent license.

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Bob Fries email:
Account Manager
MAGMA Tel: (800) 285-8990
6725 Mesa Ridge Road #100, (619) 457-0750
San Diego, CA 92121 Fax: (619 457-0798
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>From 49.27 SunFlash:

      Revolution Technologies First To Unveil Transparent Low Cost
        Disk Compression Software For SPARC Workstation Users.
NATICK, Mass. -- January 4, 1993 -- Revolution Technologies (tm) today
introduced PowerDriveTM, a software product designed to transparently
increase the file storage capacity of SPARC workstations and servers.
With PowerDrive, users can store more files and applications at much
lower cost than purchasing additional disk drives.
The PowerDrive product is intended for users who want to store additional
applications and files on their workstations than would typically fit.
With PowerDrive, files are compressed to 50% of their original size on
average. This significant reduction virtually doubles the drive's storage
The PowerDrive software installs in minutes and allows the user to
immediately take advantage of the additional disk space. During
PowerDrive installation, existing files on the system are compressed
into the PowerDrive format -- making more room to store new files.
When a file bearing the PowerDrive format is accessed, it is
transparently decompressed for use by the user. The PowerDrive
software is fully configurable and works easily with all file types
including text files, object files, and executables.
PowerDrive is available now for the Solaris 1.0 (SunOS 4.1.x) operating
system. A version for Solaris 2.x will be available in March, 1993.
Revolution Technologies is offering a special introductory price of $99
until March 31, 1993. PowerDrive is available via anonymous FTP at
world.std.COM ( in the directory pub/revtek. Download
files powerdrive.tar and powerdrive.README.
PowerDrive can also be ordered by calling Revolution Technologies at
(508) 650-1490 or by sending a FAX request to (508) 655-8860.
Users can try out PowerDrive at no cost for 30 days by obtaining a demo
license from Revolution Technologies.
Revolution Technologies and PowerDrive are trademarks of Revolution
Technologies. SPARC is a registered trademark of SPARC International, Inc.

E-mail: Tim Littlejohn
Snail Mail: Departement de biochimie Phone: (514) 343-7936
            Universite de Montreal Fax: (514) 343-2210
            C.P. 6128, succursale A,
            Montreal (Quebec), H3C 3J7

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