ZFS

Tim Foster had sent an email to IOSUG mailing list yesterday, that tomorrow, at 7pm, Roch Bourbonnais will present a tech talk on ZFS Performance.

Here's the announcement:

So, amazingly short notice here, but we're going to hold a talk on ZFS Performance this Wednesday.

Roch Bourbonnais, an expert on kernel performance is visiting Dublin on Wednesday and we thought we'd take the opportunity to hear more about ZFS internals & performance from him.

Roch has been examining ZFS in great detail during it's development with a view to it's characteristics on real-world workloads. If you're interested in ZFS, or have heard about it but want to know more, you really should come along on Wednesday.

More information on Roch's background and experiences with ZFS so far at http://blogs.sun.com/roch/

Again, our apologies for the short notice.

All the details are on the official IOSUG8 invitation page.

At last, I see some real progress with available translations of excellent Solaris docs!

For instance, ZFS administration guide in Russian was posted on the OpenSolaris/G11 (Globalization) Consolidation page just a few days ago.

It really is great to see great translations like this completed. Well done, guys!

I'm considering getting myself an x86 server with Solaris for home use, and today I've decided to play around with ZFS on my old Sparc-box.

I believe those of you who are just getting started with ZFS will really like the -n command line option for zfs and zpool, which allows you to see what result would a certain command yield, while there is nothing actually done to your disks.

So, if you're thinking of creating a new storage pool, you don't have to actually create it just to see how it will look - you can use -n option instead:



The command will still be validated - its syntax will be checked, plus you'll have the existance of the disks verified as well. So, if you don't have one of the devices in your system, you might see something like this:

There is quite a number of ZFS filesystems properties, and I will cover most useful ones today.

I'll begin with refreshing your knowledge a bit. As I've told before, I'm going to create a number of ZFS filesystems on my server for the next few blog entires on ZFS. So, right now I have the following:


To get a value of some ZFS property, we normally use a command like this:


But such output isn't always convenient for us - it's formatted this way to make the data more human readable. But if we're going to use zfs get to obtain some ZFS parameters from our scripts, we really don't need anything fancy. So we're probably better off using a special -H command line option:


One more thing - a useful, yet very obvious feature which allows you specifying few properties names in one command line:


Okay, now let's move on and look at some useful ZFS filesystems properties.

For instance, the mountpoint property name speaks for itself. By default, the filesystem which you change the mountpoint for, will be automatically remounted at a new location:



One more potentially useful option is an on-disk compression. It happens on the fly, and it is planned to eventually have a number of compression methods available to a ZFS administrator, but at the moment you can use only one method - lzjb.

Still, results are impressive:


No wonder the compression ratio is so good for this filesystem:


Unfortunately, only few types of files can be so wonderfully compressed, and text files (for instance, my Apache2 logs) belong to them too. Executable files, of course, will compress with a much lower ratio.

I think that should do for today's entry. Let me tell you right now: I have a whole series of ZFS blog entries planned ahead, and that's the reason I haven't covered some of the simpler ZFS filesystem options yet. I promise to write more in the nearest few days.

Hi!

Unbelievable - this turns out to be the very first entry of mine in 2006! I couldn't postpone new entires anymore, so here's one for you :)

It's been quite a while since I've cleared one of internal disks in my Netra t105 to bring it under ZFS control. As a result, I now have a 33Gb zfs-pool to experiment with. Today I had some spare time, so I've decided to share the very basics of managing ZFS filesystems.

So this is the pool I have:



And like I said, it has only one drive in it:


By default, when you create a zfs-pool, all of its disk space is represented as a single filesystem with the same name. This filesystem also gets a mountpoint with the same name and is automatically mounted off /. So, after doing a zpool create (here is my example) you can immediately start working with your newly made filesystem.

At the moment I've got only 1 additional filesystem created, I use it for Oracle 10g. So here's how it looks:


According to ZFS concepts, all the newly made filesystems may use all the available disk space of the zfs-pool they belong to. So, when I create another filesystem in my stock pool, this filesystem has more than 30Gb available to it:


To make sure that some of your filesystems don't eat up all the available disk space, you have to limit them. And it's very easily done so:


As you have probably guessed, quota is the parameter name, while set is a keyword to alter parameters values. There is quite a number of ZFS filesystem parameters, and most of them you can modify, but there are also some which are read-only. Here's an example of such a parameter, and you can see what happens if you try modifying them:


You can find the full list of ZFS filesystem parameters on the man page for zfs, as for me - I'll show you only 1 more parameter today, and a very useful one in my opinion: a mount point. As all the rest things about ZFS, this parameter is very easy to change, and you even have the filesystem automatically remounted for you:


I left the df output intentionally here, to show that there were no additional manipulations made to the try filesystem - it really is this easy!

I guess that's enough for today - so next time I'll tell you about few more useful ZFS filesystem parameters. Good luck with your experiments!