[MLUG] A mini blog about file systems.

[Leslie Satenstein]

Stefan,

It could very well be that the footprint for ext4 is about the same as ext3.  However, always in the system is ext2, required for the boot partition. 

So, ext3 just adds some journalling.  As far as I know, ext4 is incompatible with ext[23].




-------------
Regards  
Leslie
 Leslie Satenstein
5752 Avenue Lockwood.
Cote St. Luc Montreal Quebec H4W 1Y9  Canada
voice:  514-369-1685    
mailto:lsatenstein at yahoo.com 

--- On Sun, 3/22/09, Stefan Monnier <monnier at iro.umontreal.ca> wrote:

From: Stefan Monnier <monnier at iro.umontreal.ca>
Subject: Re: [MLUG] A mini blog about file systems.
To: "Montreal Linux Users Group" <mlug at listserv.mlug.ca>
Date: Sunday, March 22, 2009, 4:28 PM

> If I have a small desktop computer with perhaps 512megs of memory and
> an 80 gig drive, what do I want to have loaded in memory so as to have
> the maximum amount of free memory available for my application?

Does anybody here have some hard-data comparing the amount of RAM
used up by various filesystems, and/or LVM?

FWIW, I'm using LVM on all my machines, except for my cellphone.
I.e. this includes my "home router" and its 64MB of RAM (driving a 1TB
drive).  Those 64MB are pretty tight, but I haven't noticed any
difference in memory pressure when I (recently) moved to LVM.

> and as little extra for the kernel.  Would EXT4 be best? That is my
> thought.

Why would ext4 be better than ext3 for this case?
Why would these same reasons not apply to a laptop?

> BTFRS in theory will replace LVM.

I don't know if/that btrfs will replace LVM.  It might be true that if
you use btrfs, you may not gain much by combining it with LVM, but btrfs
is a monster, which will tend to limit its popularity.

> Finally, in the articles I read, the new hard disks come with 16megs
> or even 32 megs of cache memory.  Not one author has been written
> about using ext[234], lvm or btfrs with these devices.

I'm not sure I understand what you wrote (I'll just assume that you
meant "article" rather than "author").  But I don't think the disk's
cache makes much difference to the choice of filesystem (there is even
little evidence that it makes much difference about anything at all:
it's important to have some cache there, used for prefetching and
write-caching, but its size is not critical: the main disk cache is in
the main memory, where it can easily grow much larger than 32MB and can
be "cheaply" increased).


        Stefan
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