Re: How efficient is mounting /usr ro?
On Wed, 26 Nov 2003 14:24, Bernd Eckenfels
<ecki@calista.eckenfels.6bone.ka-ip.net> wrote:
> > I am talking about any file system. When only reading from a file system
> > there should not be any performance difference when comparing a RO mount
> > vs a NOATIME mount. If there is a difference then it's a bug in the file
> > system.
>
> I guess the thread was about non-journalling filesystems beeing faster, and
> less of a risk if used ro.
Even for a non-journalling file system there should be no risk. If a file
system is mounted and never written to then only a single disk block should
change, the one with the dirty bit indicating that an fsck might be needed on
a reboot. If that block is corrupted then you may need to use the backup
superblock in the worst-case, but that would require a crash while mounting
the file system.
> > The difference it makes is that reading from the disk will never cause
> > disk writes. If you access large numbers of files or if you have IO
> > hardware that has a bottleneck of write bandwidth (EG a typical mail
> > server) then NOATIME makes a significant difference.
>
> News Servers are even worth. And full-filesystem scans and some backup
> tools make the a-time less usefull anyway.
There should be a way of reading a file without changing the ATIME that backup
programs can use.
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