[Gluster-users] gluster ha/replication/disaster recover(dr translator) wish list

[Keith Freedman]

I just wanted to toss out a thought I had to get it on the table.

For me, the replication features (in any filesystem that supports it) 
serve several purposes

1, is to have 2 or more copies of the data which are live and useable 
(I think lustre doesn't offer this) -- this is handy for HA, and for 
performance (in my case, the servers are clients, and so they read 
data from their local disk and only have to go down to network speed 
when writing).

another is for disaster recovery.

What I'd like to see is a DR translator..  which is basically 
identical to AFR with a few notable exceptions:
1) it would be a one-way pipe--when data is updated, the updates are 
pushed over, and it's assumed that the DR location is never written 
to locally, so the auto-healing can make some assumptions and not 
have to do a 2 way comparison and data transfer
2) delayed writes -- I'd like to specify an allowable delay for 
updates (if this is 0, then my writes will block waiting on the data 
to be replicated), if this is higher, then gluster returns control 
back after it's written the file to the "local brick" but then 
replicates in the background.
3) delayed writes 2 --  if we're allowing delayed writes, then there 
may be an added benefit.  if the same file changes multiple times 
over a short period, we only have to transfer the most recent version 
of that data across the network.

So, one could have a disaster recovery site with slower Internet 
connections which are in sync within a specified amount of time.  Or 
one could even use a service like Amazon S3 as a repository without 
worrying about super huge data transfer fees.

I could see it used to manage a file-serving/web farm.  For example:
I might have 7 machines which just serve images and videos.  I update 
them by pushing a new image/video to one master server, the other 6 
get updated.

If someones updated a file on the DR box (i.e. the auto-heal would be 
triggered) instead of the file on the DR box being replicated back, 
it should be over-written with the version of the file on the master.

This would insure data integrity and you could put your master copy 
of files on a very hardened secure server behind a firewall or DMZ, 
and if someone breaks into a box and tries to overwrite an image or 
something it would automatically get 'healed' from the master copy.

Then, if there is a disaster, and you're running from your DR site, 
you simply reverse the configuration, and after the disaster let 
things auto-heal the other direction and then switch back once things 
are in sync.

those are my thoughts.
Keith