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Ignazio Palmisano ignazio_io at yahoo.it
Wed May 13 15:57:07 BST 2009


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.




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