Can I setup a logical volume to be compressed?

[PRIMS Central]

Is it possible to set-up a logical volume so that every file on it is compressed/uncompressed automatically? Something similar with what Microsoft Windows can do?
IF yes, does it need to be a new logical volume or can I do this with an existing logical volume?

I am using basic JFS LVM on HP-UX 11.0.

[Patrick Wallek]

No. As far as I know there is no way to do this.

[Steven E. Protter]

I've looked through newfs -o options and don't see anything.

You could run a cron job that compresses or gzips any file thats not zipped, but the overhead would be terrible.

SEP

[A. Clay Stephenson]

No, unfortunately unlike advanced operating systems like Windows, HP-UX has no provision for compressed filesystems. Linux does have loopback filesystems with the hooks to make this possible but HP-UX does not.

The UNIX view of the world is that disk is cheap and performance is everything. Why impose performance hits when it's so easy to add disk space.

[Leif Halvarsson_2]

Hi,
It is no automatic compress/uncompress in HP-UX as in Windows or Netware. And not in any other UNIX dialect (as far as I know). And even in high end 3-party products (as Veritas filesystem/Volume manager) there is no such utility.

I don't know the reason but I think the risk for teouble is one, what happends if there is no space left on the filesystem when a file needs to be uncompressed ?

[Jeff Schussele]

Hi,

Yep, us poor UNIX SAs are stuck with those awfully high TPS values & those interminably long uptimes. Sheesh, we can't even squeeze in a reboot here & there. The pasky things just keep running like the Enegizer bunny 8~))

Cheers,
Jeff

P.S. The only way to do this would be a home-grown app, BUT I certainly would NOT recommend it.

[Pete Randall]

I suppose you could set up a cron job to periodically compress everything in the subject directory but that's not going to automatically uncompress.


Pete

[Shannon Petry · Accepted solution]

No, and I dont recommend it for many many reasons.

1. Impact on other critical I/O: Tape devices will compress non compressed data only. This is a case where I/O is not as impacted by uncompressing streams of data. Backups are critical, and tapes write performance is never as good as a disk. makes more sense to compress at this level.

2. Performance: Ever wonder why Netapps, Veritos, UFS(Sun), JFS(IBM), VxFS(HP), XFS(Irix) do not do use compression streams for Disk I/O? It impedes performance. Even if it's 1% degredation in performance, when your capable of pushing GB a sec as opposed to MS and Craptel IRQ technology pushing low hundreds of MB a sec, it's a huge difference. Imagin how bad my FEA would look, running constant disk I/O, reading and writing hundreds of GB. My 1/2 hour jobs quickly turn into hour jobs, and imagine the impact on my week long simulations in PamCrash... Ugh...

3. Integrity: The only to have the very low 1% margin on performance is to use hardware compression. Data is now buffered 2 times, 1 time for compression, 1 time for write. Write cache is recoverable, but compression is not. There is no way to track the state a file was in when partially compressed. In an adverse situation, data would be compromized.

Just remember that if MS does it, it does not make it good. (reflect on Netbios and how MS thought it would take over the world and the internet would flop). MS does things for the desktop casual user, so they can look good. They care for squat about performance beyond gaining market share. Lord knows they did that with web servers, but people quickly learned that linux is a much better approach. (MS down 30% in the server market in the last 2 years).

Disks are cheap, and will continue to get cheaper. Just add a disk when your files systems are full, or have users clean up that 7year old data they still have in their home directories ;)


Regards,
Shannon

[Caesar_3]

Hello!

As far as i know there is no such feature that came built in the HPUX OS.

In the linux world you have devices that you work through them the compres/decompres the data and also encode/decode by password.

I taked the source from linux and compiled it for HPUX 11i but after i try to run it i have errors to work!

But if you use this type of compresion devices you lose preformance so you shuld think first you you want this.

In linux the preformance is OK because the kernel support this thing but HP not support this.

Caesar

[BIHAN]

I'm not sure that there is any solution for HP-UX but here are some information about the subject.

http://www.almondseed.com/
they did it for solaris via a patched nfs server.

http://www-sor.inria.fr/old-sor/mirrors/usenix2001/full_papers/zadok/zadok_html/index.html
A USENIX paper on the same idea.