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Re: Disabling atime



On Fri, 2007-08-10 at 07:59 -0400, James Hubbard wrote:
> On 8/9/07, Ralf Corsepius <rc040203 freenet de> wrote:
> > IMO, disabling atime by default, just because 99% of applications, don't
> > use it, is short-sighted. It basically ditches a fundamental feature of
> > unix filessystems and converts there behavior to "DOS'ish".
> 
> If it's such a fundamental feature that should be kept around, why
> have NFS optimization documents always recommended disabling atime
> updates especially on servers where there is a lot of throughput?
I don't know.

> Just because it's a fundamental feature doesn't mean that it has to be
> used. Fundamentally, my CPU can run at 2GHz all of the time that
> doesn't mean that it should.  If 99% of the applications can do
> without it and probably 99% of the people can as well, why not go
> ahead and get disable it.
That's what people call "arrogance of the masses". Let's kill that 1%,
if 99% don't care!

<sarcasm>
It's the same argument why people argue against utf-8, work as root
(don't need uid/gids) and don't want SELinux? 

Let's remove all of this from the kernel, single seat/single user
systems don't need all this at all.
</sarcasm>

> Those that need atime will eventually figure out how to turn it on.
> The potential for a better user experience as well possible power
> savings seems to outweigh the fundamental feature argument.

A friend of mine experimented with atime/noatime yesterday:

These were his results:

Test case: A heavy weight compiler-job

Default /etc/fstab
  real    5m18.226s
  user    4m44.557s
  sys     1m17.193s
User+Sys: 365.750

Rebooted -- all filesystems noatime,nodiratime
  real    5m4.256s
  user    4m36.841s
  sys     1m8.364s
User+Sys: 346.750

new / old = .9465

[Fedora-7, i386 on an AMD Athlon(tm) 64 X2 Dual Core Processor 3800+]

Way off from the figures the proponents of notime are reporting.

Ralf



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