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[Steven Vollom]

On Wednesday 13 May 2009 10:57:07 am Ignazio Palmisano wrote:
> Derek Broughton wrote:
> > Nils Kassube wrote:
> >> Steven Vollom wrote:
> >>> This may be impossible, but can a person have data saved to the /home
> >>> partition and the backup partition simultaneously?  That would keep
> >>> my backup current all the time.
> >>
> >> I don't think there are many programs that can save data at two
> >> different places simultaneously. A backup is usually done independently
> >> at regular intervals e.g. once a day during the night hours.
> >
> > Of course, you can use software RAID in a mirror configuration (don't ask
> > me how...).
> >
> >>> Would doing that slow the computer down?
> >
> > Yes, but not much.
> >
> >> Usually yes. Saving something to disk means waiting for the disk to
> >> complete the operation (unless you are saving only tiny bits of data).
> >> Saving to two places means waiting twice. Actually it may take less than
> >> double the time but you would notice a difference.
> >
> > It should be _much_ less than twice the time, but more than once :-)
> >
> >>> Since I have 8gb of RAM, won't that make the duplicated task
> >>> manageable?
> >>
> >> It is not a question of RAM size but waiting for the disk.
> >
> > If they're _partitions_, yes, but if they're separate disks, no.  Then
> > the disk wait time becomes basically the speed of the slower disk.
> >
> > There are also a couple of different attempts to implement an "offline
> > filesystem" via FUSE.  Google for that.  The idea is that your "ofs" is a
> > local directory hierarchy backed by another filesystem elsewhere.  When
> > you access the local filesystem, it attempts to keep it synchronized with
> > the external filesystem - if the external system is unavailable,
> > differences will be synchronized when it is next mounted.  I don't think
> > these are ready for primetime yet, but one might work in this case.
>
> I'm wondering if a simpler solution like cron + rsync would do the trick
> for Steven. The backup wouldn't be instantaneous but it could be set to
> update the backup like every couple of hours; I'm finding rsync very
> quick for updating only the changes to files, and it can be used locally
> or over the network.
>
> Now the problem is that I know nothing about using cron...
>
> I.
I have been reading, and a thing called  Vixie Cron just loads 
the files if they have changed.  That sounds like the right application.  It 
can be set to work at reboot and happens in root without having to do that 
part of getting it done.

SV