[Gluster-users] distribute replicated volume and tons of questions

[Gandalf Corvotempesta]

Some questions:

1) can I start with a simple replicated volume and then move to a
ditributed, replicated by adding more bricks ? I would like to start
with 3 disks and then add 3 disks more in next month.
seems stupid but this allow me to buy disks from different production batches.

2) let's assume (to keep it simple) a 1GB file with sharding enabled
with 100MB size.
In a replicated volume with just 1 replicated brick, all shared (and
thus the file) are placed on the brick (replicated to 3 servers).
What in case of 2 bricks ? Gluster will place shard 1 to 5 on brick1,
and 6 to 10 on brick2 or "distribution" only happen for the whole file
? (in example, all shards for file1 are placed on brick1, and all
shards for file2 are placed on brick2)

3) Based on question 2, when accessing a distributed file, gluster
will read from all disks increasing the available bandwidth and
thourhgput ?

4) Still keeping it simple, very simple: let's assume a VM with 10GB
disk image placed on a distributed replicated volume. This VM hosts a
simple webserver with a simple, but huge, website.
Users accessing the website will access different section of the
underlaying disk image.
These accesses are distributed across the 2 bricks doubling the read
performance (and write performance, as I can write on 2 disks at once)
?

5) by using ZFS, should I use a redundant ZIL ? What happens in case
of ZIL failure? Usually, some date are lost, but Gluster is replicated
in a syncronous way, thus loosing a ZIL on a single server should not
be an issue, right ? Is gluster able to recover from this
automatically ?