Re: [Gluster-devel] Crawling and indexing hardware

[Kevan Benson]

Anand Avati wrote:
> > When the server that dropped out reconnects, it's version will be higher
> > than the new (reset) version, and it's old file will clobber the new file.
>
> This is not entirely correct. This can *potentially* happen if the two
> clients (the client who created the first file and the client which
> re-created the file) are out of sync in time. AFR keeps the client system
> create time in the xattr and uses that as a major version number (the other
> thread discusses changing this major number to be equal to the parent dir
> minor number).
>
> If time(system1) - time(system2) < wall_time(file1) - wall_time(file2) then
> there is no data corruption.

Again we come back to the issue of the servers needing their time 
synced.  I keep thinking that some way to provide a stabilized agreed 
upon time for all cluster members would do away with this problem.  NTP 
might just not be as good a solution as something provided in cluster, 
because then AFR members could decide to not participate if they 
couldn't agree and sync to the cluster time.

Also, to what precision is the time saved?  I can imagine modify, move 
and create operations happening in quite a short time period.  Short 
enough to be sub second if that's the only precision being kept, or 
possibly within the drift of ntp synced systems for sub second precision.


--

-Kevan Benson
-A-1 Networks