[Sheepdog] Use a dedicate nic for sync and other questions

[MORITA Kazutaka]

At Fri, 2 Sep 2011 14:23:53 +0200,
Valerio Pachera wrote:
> 
> 2011/9/1 Dan Luedtke <maildanrl at googlemail.com>:
> > Do you use dedicated NIC for syncing?
> 
> No and I was wondering the way to achive that.
> I guest by the parameter "bindnetaddr" in /etc/corosync/corosync.conf right?
> Using the address of a nice that is not the one I bridge with qemu-kvm.
> 
> I was also wondering if this scenario is possible:
> sda6 /mnt/sheep_data1  -> sync by eth0
> sdb6 /mnt/sheep_data2  -> sync by eth1
> 
> This way one disk is served by one nic.
> Do you think it's possible?

There is no way to use multiple NICs now; all the sheep daemons use
only one NIC which is specified in corosync.conf, and data
synchronization is done through the same NIC.

I think it is a good idea to support specifying interfaces used for
normal I/Os and object recovery.  For example:

  $ sheep /store_1 --nic io:eth0 --nic sync:eth1
  $ sheep /store_2 --nic io:eth2 --nic sync:eth3

> 
> PS:
> I think it's not the best Idea to have more than one sheepdog
> directory per node, becaus if the node goes down, much more data goes
> down too!

But even if you use RAID0, the capacity of the node will increase and
Sheepdog should allocate much more data to the node.

> A good shenario for me is 3 nodes with 2 disks each that form raid 0
> md device and 2 gigbit nics.
> This way the sync could use the full speed of a dedicated nic (1Gbit ~
> 125MB/s) without full fill the disk I/O capacity.
> A "normal" sata disk has 60-80 MB/s write speed, a raid 0 is double,
> so close to or more than max theorical nic speed.

But if you run two sheeps daemon, the I/Os will be distributed over
two disks.  If we can specify a nic for each daemon, I think there is
no big difference between using RAID0 and running multiple sheeps.

Thanks,

Kazutaka

> 
> node1 (sda/sdb) -> eth0 sync
>                         -> eth1 bridge for kvm guests
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