[Sheepdog] Option 'copies'

[Valerio Pachera]

2011/8/22 MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp>:
> I'm not sure this answers your questions, but currently you need to
> run multiple sheep daemons to handle multiple directories.

"Multiple sheep daemons" means run more time 'sheep <dorectory>" right?

I did this: created a cluster on two nodes.
storage1  'sheep /sheep_data' (sda6)
storage2  'sheep /sheep_data' (sda6)

I run a vm and chunks have been writen on the two directories.

Then I added two directories:
storage1 'sheep /sheep_data2' (sdb6)
storage2 'sheep /sheep_data2' (sdb6)

No data have been writen in these last two directories.
I also run 'dd if=/dev/zero of=tmp bs=1M count=2048' on the vm to make it grow.

Are the last two directories going to be used when no space is lefet
on the firts two?



>> If I shutdown a node after the other...
> As you may know, you should run "collie cluster shutdown" before
> stopping a Sheepdog cluster to avoid extra data copies..

No, I didn't know. Honestly I do no have very clear how sheepdog
manage the chunks when a node goes down (e.g. black out).
Or better: I aspect sheepdog to find out the chunks that have a single
copy and replicate them in the available nodes.
What is less clear to me is: what happens when the node comes up again?
In the scenario of 3 nodes with copies=2, the third node goes down for
some time; it's data should be replicated on the two nodes left; when
it's back, it still have the 'old' chunks (some might be changed, some
not)...
So we have extra redoundance for some chunks plus some 'old/trash' chunks.
How does sheepdog manage this?
What happens when I do "collie cluster shutdown"?

Thank you for the answers.