I've got a virtual server running MySQL where I'm going to convert the Dom0 to ZFS. Currently the Dom0 exports a LVM volume to the DomU which uses Ext4 for the database. My options are to use a ZFS zvol instead of a LV for the Ext4 filesystem or to use a ZFS filesystem that is NFS exported.
Using LVs for DomUs decreases space efficiency as each separate block device needs to have adequate free space. It also makes backups a little more inconveniant as the block device needs to be snapshotted and mounted in the Dom0 instead of just using regular file access or ZFS filesystem snapshot plus regular file access. I expect that both of these options will give a greater latency than the current situation. It's either NFS latency or Ext4 latency on top of ZFS latency as opposed to just Ext4 latency on it's own. As write latency is probably the main performance criteria for a database which is heavily dependent on synchronous writes this would surely be a problem in some situations. However in this case the server averages 71KB/s of writes for 24*7 operation with iowait always staying below 4% so I don't think that a drop in performance is going to cause any problems. What do you think? -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/ _______________________________________________ luv-main mailing list [email protected] http://lists.luv.asn.au/listinfo/luv-main
