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Re: [zfs-discuss] Slow death-spiral with zfs gzip-9 compression

Subject: Re: [zfs-discuss] Slow death-spiral with zfs gzip-9 compression
From: Mario Goebbels
Date: Sat, 29 Nov 2008 18:33:56 +0100
> I expect it will go SO SLOW, that some function somewhere is eventually
> going to fail/timeout.  That system is barely usable WITHOUT
> compression.  I hope at the very least you're disabling every single
> unnecessary service before doing any testing, especially the GUI.
> ZFS uses ram, and plenty of it.  That's the nature of COW.  Enabling
> realtime compression with an 800mhz p3?  Kiss any performance, however
> poor it was, goodbye.

Regardless of that, gzip is still heavy on the system. Unbz2ing a 30MB
package (e.g. VirtualBox) in my packages ZFS filesystem with gzip
compression does affect interactivity quite a lot (i.e. 1 sec UI freezes
on transaction commit). This on an Intel Core2 Quad!

I do not notice these effects using lzjb.

People have been clamoring for lzo support more than a year ago. That
algorithm gets a decent compression rate not far from gzip and has a
very light footprint similar to lzjb. I think someone even wanted to
start a project for porting alternative compression methods to ZFS,
focusing on BWT tho, but nothing came from that (at least publicly).


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