Linked by Thom Holwerda on Fri 23rd Oct 2009 21:13 UTC, submitted by poundsmack
Mac OS X John Siracusa, the Mac OS X guru who writes those insanely detailed and well-written Mac OS X reviews for Ars Technica, once told a story about the evolution of the HFS+ file system in Mac OS X - he said it was a struggle between the Mac guys who wanted the features found in BeOS' BFS, and the NEXT guys who didn't really like these features. In the end, the Mac guys won, and over the course of six years, Mac OS X reached feature parity - and a little more - with the BeOS (at the FS level).
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RE: ZFS memory hog?
by fridder on Mon 26th Oct 2009 17:31 UTC in reply to "ZFS memory hog?"
fridder
Member since:
2007-11-03

Also, keep in mind that the high memory usage is also due to very aggressive caching on ZFS's part

Reply Parent Score: 1

RE[2]: ZFS memory hog?
by sbergman27 on Mon 26th Oct 2009 18:22 in reply to "RE: ZFS memory hog?"
sbergman27 Member since:
2005-07-24

Also, keep in mind that the high memory usage is also due to very aggressive caching on ZFS's part

There is something about all of this that I have never understood. The linux page cache and buffer cache make aggressive use of memory for caching. To a great extent, application pages and disk data are treated the same. (Though not exactly the same. e.g. /proc/sys/vm/swappiness.) And yet when more memory is needed for applications, it is available in a flash. Thus no one ever speaks of Linux filesystems as having a memory *requirement*. What flusters me about ZFS is all this talk about it having a memory *requirement*. A filesystem should not have a memory *requirement*.

Is this an artifact of the strange way that ZFS was implemented? i.e. a result of it being a "rampant layering violation", as Andrew Morton once quipped? In Linux all that sort of caching, for all block devices, as well as applications, takes place in one unified layer. But in ZFS, I guess it allocates large amounts of memory and does its own management of it, independent of the rest of the kernel?

Edited 2009-10-26 18:25 UTC

Reply Parent Score: 2

RE[3]: ZFS memory hog?
by Kebabbert on Tue 27th Oct 2009 10:10 in reply to "RE[2]: ZFS memory hog?"
Kebabbert Member since:
2007-07-27

ZFS releases all memory as soon as an application needs RAM. The thing is, to achieve good performance you need at least 1GB RAM and 64bit CPU. If you have 512MB RAM or 32 bit CPU then the performance will not be so good.

I used 1GB RAM and 32bit CPU and I only got 20-30MB/sec with 4 discs. With 64 bit CPU, I get over 100MB/sec. ZFS is 128 bits, so it likes 64bit CPUs.

So, ZFS does not _require_ much ram nor 64 bit CPU, but your performance will not be good without them.

Reply Parent Score: 2