Sysadmin

As I've been investigating ZFS for use on production systems, I've been making a great deal of notes, and jotting down little "cookbook recipies" for various tasks. One of the coolest systems I've created recently utilised the zfs send & receive commands, along with incremental snapshots to create a replicated ZFS environment across two different systems. True, all this is present in the zfs manual page, but sometimes a quick demonstration makes things easier to understand and follow.

While this isn't true filesystem replication (you'd have to look at something like StorageTek AVS for that) it does provide periodic snapshots and incremental updates; these can be run every minute if you're driving this from cron - or, at even more granular intervals if you write your own daemon. Nonetheless, this suffices for disaster recovery and redundancy if you don't need up-to-the second replication between systems.

I've typed up my notes in blog format so you can follow along with this example yourself, all you'll need is a Solaris system running ZFS. Read more for the full demonstration...

Continue reading "ZFS Replication"

While browsing the ZFS man page recently, I made an interesting discovery: ZFS can export block devices from a zpool, which means you can separate "ZFS the volume manager" from "ZFS the filesystem". This may well be old news to many; however I haven't seen many references to this on the web, so thought I'd post a quick blog update.

The example used in this post is the creation of a mirrored zpool which is then used to create a block device, on top of which I'll create a UFS filesystem. The reasons for doing this are many and varied : you may have an application that needs UFS (particularly forcedirectio); you may need to create a block device for some reason but all your storage is currently tied up in zpools; or you just need a quick block device to use for testing.

Using ZFS as a volume manager also has it's advantages over something like SVM (formerly "DiskSuite"). The management features are much improved (along with a browser-based GUI, if that's your thing) and you also gain access to ZFS features which operate at the volume manager layer and aren't dependant on the filesystem parts of ZFS. This includes features such as end-to-end error checking and recovery, along with snapshots.

Read on for the full update...

Continue reading "ZFS as a volume manager"