Zookeeper: configure 'dataLogDir' in separate disk

[gyuho]

http://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_advancedConfiguration

Having a dedicated log device has a large impact on throughput and stable latencies. It is highly recommened to dedicate a log device and set dataLogDir to point to a directory on that device, and then make sure to point dataDir to a directory not residing on that device.

http://www.mail-archive.com/user@zookeeper.apache.org/msg07646.html

etcd would get separate wal, data dir as well.

TBD: Consul?

[gyuho]

This makes collecting disk metrics much more complicated, since data from separate disks need to be aggregated for comparison. This might make sense if we only test Zookeeper.

[xiang90]

It would be great if someone familiar with ZK can help on this.