HFS+ Compression: How long should it take to compress a folder?

I am using HDCleanup to apply Snow Leopard's HFS+ Compression to my user folder.

The "Compressing" window has been running with its moving blue and white barber pole for several hours now. The folder in question contains just one user's files (Desktop, Documents, etc.) and is 148 GB in size. Isn't this taking an awful long time? Since it is recommended to do this once a month, is this a process (like Time Machine) that takes hours the first time, but only a few minutes subsequently?

In other words, should I stop this process? Is it a waste of time for a user folder?

Thanks in advance....

iMac 24" early 2008, Mac OS X (10.6.3), VMWare Fusion to run Windoze

Posted on Jun 1, 2010 5:49 PM

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6 replies

Jun 1, 2010 6:37 PM in response to ColRay

IMHO, you're wasting your time. Compression slows things down, since files have to be decompressed before they can be used. Further, using HFS+ compression on every file in your user folder seems uniquely un-useful, since every file you change will become uncompressed again, requiring you to use HDCleanup to compress it again. And keep in mind that some of the larger files, like any .jpeg files and many .pdf files, will already be compressed and compressing them again may actually cause them to become larger! With disk space dirt cheap these days, is it really that big a deal to squeeze maybe a GB or two out of that 148 GB?

Also, note that many of the other functions of HDCleanup are unnecessary (see [Five Mac Maintenance Myths|http://www.macworld.com/article/133684/2008/06/maintenance_intro.html]) or even outright dangerous (in the case of slimming universal apps). This is not an app that needs a place on your hard drive.

Jun 1, 2010 7:31 PM in response to thomas_r.

Well... Thanks for the unsolicited opinion.

I guess I will wait for an actual answer to my question on how long it should take.

By the way, everything HDCleanup has done so far (with the notable exception of Application SLimming - SAY FAR AWAY FROM THIS!!!!) has freed up some 100GB of disk space and sped everything up, as advertised. I do have memory-hogging video and photos on a 1TB external Firewire 800 HD and back both my drives up on a 2TB External, via Firewire 400. This seems to be the optimum setup for me.

Jun 1, 2010 8:00 PM in response to thomas_r.

Compression slows things down, since files have to be decompressed before they can be used.

That is more a function of available CPU horsepower vs disk throughput (and whether a fragmented compressed file has fewer fragments than a fragmented uncompressed file; relates to how often the disk needs to seek in order to completely read the file).

And decompression takes less effort than compression.

Now if the storage device is a screaming SSD drive, then the balance may shift the other way.

Then again, files on a NAS that you access over WiFi would really benefit when transferred in compressed from, and decompressed on the system.

As the transfer medium gets faster, the benefit of compression with respect to speed goes down.

PS. In my day job, I am a Unix file system developer. I worry about disk access professionally 🙂

Jun 1, 2010 9:02 PM in response to BobHarris

@BobHarris:
You definitely sound like a Unix expert! At some point during the day, I had to "cancel" compression because... well it was running for 9 hours and there is no countdown meter or anything. However, my "available" disc space went from 320GB to 428 GB so it must have saved some space.

I will leave this question open to invite other comments because this is very interesting and informative.

Thanks!

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HFS+ Compression: How long should it take to compress a folder?

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