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20090108 Thursday January 08, 2009

Making 3D work over VNC

Dave recently played around with VNC on his computer and an iPod touch. While it worked surprisingly well, the achilles heel of many remote access solutions kicks in when you try doing some 3D stuff, such as a game, Second Life or maybe a scientific application.

This reminds me of one of the best kept secrets at Sun: We fixed the 3D-over-VNC problem.

International Supercomputing Conference 2008, LRZ booth showing 3D remote visualizationJust check out the Sun Shared Visualization Software, it is free and based on open source packages and it works like a charm. For example, here is a picture of the ISC 2008 conference in Dresden where you see a molecular visualization program in 3D stereo at the LRZ booth in Dresden, which is actually running in Garching near Munich.

That's right, the server runs in Munich, the client is in Dresden, there's more than 400km air line in between (probably close to double that in terms of network line) and we saw close to 30 frames per seconds of intricate molecular modeling madness that we could manipulate interactively like if the server was around the corner. In this case, the "server" was a supercomputer that fills the halls of the LRZ compute center, so it wouldn't quite fit the showfloor, thus they used Sun Shared Visualization to deliver the images, not the whole supercomputer, to Dresden.

And this is an increasingly common theme in HPC: As data amounts get bigger and bigger (Terabytes are for sissies, it's Petabytes where the fun starts) and compute clusters get bigger and bigger (think rows of racks after racks), your actual simluation becomes harder to transport (a truck is still the cheapest, fastest and easiest way to transmit PB class data across the nation). The key is: You don't need to transport your data/your simulation/your research. You just need to show the result, and that is just pictures.

Even if it's 3D models at 30 frames per second (= interactive speed) with 1920x1080 pixels (= HDTV) each frame, that's only about 180MB per second uncompressed. And after some efficient compressing, it boils down to only a fraction of it.

This means that you can transmit HDTV at interactive speeds in realtime across a GBE line without any noticeable degradation of image quality, or if you're restricted to 100 MBits or less, you can still choose between interactive speeds (at some degradation of picture quality) or high quality images (at some sacrifice in speed) or a mixture (less quality while spinning, hold the mouse to get the nicer picture). And this is completely independent of the complexity of the model that's being computed at the back-end server.

The Sun Shared Visualization Software is based on VirtualGL and TurboVNC, which are two open source projects that Sun is involved in. It also provides integration with the Sun Grid Engine, so you can allocate multiple graphics cards and handle reservations like "I need 3 cards on Monday, 3-5 PM for my presentation" automatically.

So, if you use a 3D application running on Linux or Solaris and you want to have access to it from everywhere, check out the Sun Shared Visualization Software for free and let me know what you've done with it. Also, make sure to check out Linda's blog, she runs the developer team and would love to get some feedback on what people are using it for.

P.S.: There's some subtle irony in the LRZ case. If you check their homepage, their supercomputer has been built by SGI. But their remote visualization system has been built by Sun. Oh, and we now have some good supercomputer hardware, too.

"Making 3D work over VNC" has been brought to you by Constantin's Blooog.
This entry was created on 2009-01-08 05:31:27.0 PST and is associated with the following tags:

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20080320 Thursday March 20, 2008

How to compile/run MediaTomb on Solaris for PS3 and other streaming clients

MediaTomb showing photos on a PS3Before visiting CeBIT, I went to see my friend Ingo who works at the Clausthal University's computing center (where I grew up, IT-wise). This is a nice pre-CeBIT tradition we keep over the years when we get to watch movies in Ingo's home cinema and play computer games all day for a weekend or so :).

To my surprise, Ingo got himself a new PlayStation 3 (40GB). The new version is a lot cheaper (EUR 370 or so), less noisy (new chip process, no PS2 compatibility), and since HD-DVD is now officially dead, it's arguably the best value for money in Blu-Ray players right now (regular firmware upgrades, good picture quality, digital audio and enough horsepower for smooth Java BD content). All very rational and objective arguments to justify buying a new game console :).

The PS3 is not just a Blu-Ray player, it is also a game console (I recommend "Ratchett&Clank: Tools of Destruction" and the immensely cute "LocoRoco: Cocoreccho!", which is a steal at only EUR 3) and can act as a media renderer for DLNA compliant media servers: Watch videos, photos and listen to music in HD on the PS 3 from your home server.

After checking out a number of DLNA server software packages, it seemed to me that MediaTomb is the most advanced open source one (TwonkyVision seems to be nicer, but sorry, it isn't open source...). So here is a step-by-step guide on how to compile and run it in a Solaris machine.

Basic assumptions

This guide assumes that you're using a recent version of Solaris. This should be at least Solaris 10 (it's free!), a current Solaris Express Developer Edition (it's free too, but more advanced) is recommended. My home server runs Solaris Express build 62, I'm waiting for a production-ready build of Project Indiana to upgrade to.

I'm also assuming that you are familiar with basic compilation and installation of open source products.

Whenever I compile and install a new software package from scratch, I use /opt/local as my base directory. Others may want to use /usr/local or some other directory (perhaps in their $HOME). Just make sure you use the right path in the --prefix=/your/favourite/install/path part of the ./configure command.

I'm also trying to be a good citizen and use the Sun Studio Compiler here where I can. It generally produces much faster code on both SPARC and x86 architectures vs. the ubiquitous gcc, so give it a try! Alas, sometimes the code was really stubborn and it wouldn't let me use Sun Studio so I had to use gcc. This was the path of least resistance, but with some tinkering, everything can be made to compile on Sun Studio. You can also try gcc4ss which combines a gcc frontend with the Sun Studio backend to get the best of both worlds.

Now, let's get started!

MediaTomb Prerequisites

Before compiling/installing the actual MediaTomb application, we need to install a few prerequisite packages. Don't worry, most of them are already present in Solaris, and the rest can be easily installed as pre-built binaries or easily compiled on your own. Check out the MediaTomb requirements documentation. Here is what MediaTomb wants:

  • sqlite3, libiconv and curl are available on BlastWave. BlastWave is a software repository for Solaris packages that has almost everything you need in terms of pre-built open source packages (but not MediaTomb...). Setting up BlastWave on your system is easy, just follow their guide. After that, installing the three packages above is as easy as:
    # /opt/csw/bin/pkg-get -i sqlite3
    # /opt/csw/bin/pkg-get -i libiconv
    # /opt/csw/bin/pkg-get -i curl

  • MediaTomb uses a library called libmagic to identify file types. It took a little research until I found out that it is part of the file package that is shipped as part of many Linux distributions. Here I'm using file-4.23.tar.gz, which seems to be a reasonably new version. Fortunately, this is easy to compile and install:

    $ wget ftp://ftp.astron.com/pub/file/file-4.23.tar.gz
    $ gzip -dc  file-4.23.tar.gz | tar xvf -$ cd file-4.23
    $ CC=/opt/SUNWspro/bin/cc ./configure --prefix=/opt/local
    $ gmake
    $ su
    # PATH=$PATH:/usr/ccs/bin:/usr/sfw/bin; export PATH; gmake install

    Notice that the last step is performed as root for installation purposes while compilation should generally be performed as a regular user.

  • For tag extraction of MP3 files, MediaTomb uses taglib:
    $ wget http://developer.kde.org/~wheeler/files/src/taglib-1.5.tar.gz
    $ cd taglib-1.5
    $ CC=/usr/sfw/bin/gcc CXX=/usr/sfw/bin/g++ ./configure --prefix=/opt/local
    $ gmake
    $ su
    # PATH=$PATH:/usr/ccs/bin:/usr/sfw/bin; export PATH; gmake install

  • MediaTomb also uses SpiderMonkey, which is the Mozilla JavaScript Engine. Initially, I had some fear about having to compile all that Mozilla code from scratch, but then it dawned on me that we can just use the JavaScript libraries that are part of the Solaris Firefox standard installation, even the headers are there as well!

That was it. Now we can start building the real thing...

 Compiling and installing MediaTomb

Now that we have all prerequisites, we can move on to downloading, compiling and installing the MediaTomb package:

  • Download the MediaTomb source from http://downloads.sourceforge.net/mediatomb/mediatomb-0.11.0.tar.gz
  • Somehow, the mediatomb developers want to enforce some funny LD_PRELOAD games which is uneccesary (at least on recent Solaris versions...). So let's throw that part of the code out: Edit src/main.cc and comment lines 128-141 out by adding /* before line 128 and */ at the end of line 141.
  • Now we can configure the source to our needs. This is where all the prerequisite packages from above are configured in:
    ./configure
    --prefix=/opt/local --enable-iconv-lib --with-iconv-h=/opt/csw/include
    --with-iconv-libs=/opt/csw/lib --enable-libjs
    --with-js-h=/usr/include/firefox/js --with-js-libs=/usr/lib/firefox
    --enable-libmagic --with-magic-h=/opt/local/include
    --with-magic-libs=/opt/local/lib --with-sqlite3-h=/opt/csw/include
    --with-sqlite3-libs=/opt/csw/lib
    --with-taglib-cfg=/opt/local/bin/taglib-config
    --with-curl-cfg=/opt/csw/bin/curl-config

    Check out the MediaTomb compile docs for details. One hurdle here was to use an extra iconv library because the MediaTomb source didn't work with the gcc built-in iconv library. Also, there were some issues with the Sun Studio compiler, so I admit I was lazy and just used gcc instead. 

  • After these preparations, compiling and installing should work as expected:
    gmake
    PATH=$PATH:/usr/ccs/bin:/usr/sfw/bin; export PATH; gmake install

Configuring MediaTomb

Ok, now we have successfully compiled and installed MediaTomb, but we're not done yet. The next step is to create a configuration file that works well. An initial config will be created automatically during the very first startup of MediaTomb. Since we compiled in some libraries from different places, we either need to set LD_LIBRARY_PATH during startup (i.e. in a wrapper script) or update the linker's path using crle(1).

In my case, I went for the first option. So, starting MediaTomb works like this:

LD_LIBRARY_PATH=/opt/csw/lib:/opt/local/lib:/usr/lib/firefox
/opt/local/bin/mediatomb --interface bge0 --port 49194 --daemon
--pidfile /tmp/mediatomb.pid
--logfile=/tmp/mediatomb.log

Of course you should substitute your own interface. The port number is completely arbitrary, it should just be above 49152. Read the command line option docs to learn how they work.

You can now connect to MediaTomb's web interface and try out some stuff, but the important thing here is that we now have a basic config file in $HOME/.mediatomb/config.xml to work with. The MediaTomb config file docs should help you with this.

Here is what I added to my own config and why:

  • Set up an account for the web user interface with your own user id and password. It's not the most secure server, but better than nothing. Use something like this in the <ui> section:
    <accounts enabled="no" session-timeout="30">
      <account user="me" password="secret"/>
    </accounts>
  • Uncomment the <protocolInfo> tag because according to the docs, this is needed for better PS3 compatibility.
  • I saw a number of iconv errors, so I added the following to the config file in the import section. Apparently, MediaTomb can better handle exotic characters in file names (very common with music files) with the following tag:
    <filesystem-charset>ISO-8859-1</filesystem-charset> 
  • The libmagic library won't find its magic information because it's now in a nonstandard place. But we can add it with the following tag, again in the import section:
    <magic-file>/opt/local/share/file/magic</magic-file>

  • A few mime types should be added for completeness:

    <map from="mpg" to="video/mpeg"/>
    <map from="JPG" to="image/jpeg"/>
    <map from="m4a" to="audio/mpeg"/>

    Actually, it should "just work" through libmagic, but it didn't for me, so adding theses mime types was the easiest option. It also improves performance through saving libmagic calls. Most digital cameras use the uppercase "JPG" extension and MediaTomb seems to be case-sensitive so adding the uppercase variant was necessary. It's also apparent that MediaTomb doesn't have much support for AAC (.m4a) even though it is the official successor to MP3 (more than 95% of my music is in AAC format, so this is quite annoying).

  • You can now either add <directory> tags to the <autoscan> tags for your media data in the config file, or add them through the web interface.

MediaTomb browser on a PS3This is it. The pictures show MediaTomb running in my basement and showing some photos through the PS3 on the TV set. I hope that you can now work from here and find a configuration that works well for you. Check out the MediaTomb scripting guide for some powerful ways to create virtual directory structures of your media files.

MediaTomb is ok to help you show movies and pictures and the occasional song on the PS3 but it's not perfect yet. It lacks support for AAC (tags, cover art, etc.) and it could use some extra scripts for more comfortable browsing structures. But that's the point of open source: Now we can start adding more features to MediaTomb ourselves and bring it a few steps closer to usefulness.

"How to compile/run MediaTomb on Solaris for PS3 and other streaming clients" has been brought to you by Constantin's Blooog.
This entry was created on 2008-03-20 15:07:08.0 PST and is associated with the following tags:

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20070906 Thursday September 06, 2007

7 Easy Tips for ZFS Starters

So you're now curious about ZFS. Maybe you read Jonathan's latest blog entry on ZFS or you've followed some other buzz on the Solaris ZFS file system or maybe you saw a friend using it. Now it's time for you to try it out yourself. It's easy and here are seven tips to get you started quickly and effortlessly:

1. Check out what Solaris ZFS can do for you

First, try to compose yourself a picture of what the Solaris ZFS filesystem is, what features it has and how it can work to your advantage. Check out the CSI:Munich video for a fun demo on how Solaris ZFS can turn 12 cheap USB memory sticks into highly available, enterprise-class, robust storage. Of course, what works with USB sticks also works with your own harddisks or any other storage device. Also, there are great ZFS screencasts that show you some more powerful features in an easy to follow way. Finally, there's a nice writeup on "What is ZFS?" at the OpenSolaris ZFS Community's homepage.

2. Read some (easy) documentation

It's easy to configure Solaris ZFS. Really. You just need to know two commands: zpool (1M) and zfs (1M). That's it. So, get your hands onto a Solaris system (or download and install it for free) and take a look at those manpages. If you still want more, then there's of course the ZFS Administration Guide with detailed planning, configuration and troubleshooting steps. If you want to learn even more, check out the OpenSolaris ZFS Community Links page. German-speaking readers are invited to read my german white paper on ZFS or listen to episode #006 of the POFACS podcast.

3. Dive into the pool

Solaris ZFS manages your storage devices in pools. Pools are a convenient way of abstracting storage hardware and turning it into a repository of blocks to store your data in. Each pool takes a number of devices and applies an availability scheme (or none) to it. Pools can then be easily expanded by adding more disks to them. Use pools to manage your hardware and its availability properties. You could create a mirrored pool for data that should be protected against disk failure and that needs fast access to hardware. Then, you could add another pool using RAID-Z (which is similar, but better than RAID-5) for data that needs to be protected but where performance is not the first priority. For scratch, test or demo data, a pool without any RAID scheme is ok, too. Pools are easily created:

zpool create mypool mirror c0d0 c1d0

Will create a mirror out of the two disk devices c0d0 and c1d0. Similarly, you can easily create a RAID-Z pool by saying:

zpool create mypool raidz c0d0 c1d0 c2d0

The easiest way to turn a disk into a pool is:

zpool create mypool c0d0

It's that easy. All the complexity of finding, sanity-checking, labeling, formatting and managing disks is hidden behind this simple command.

If you don't have any spare disks to try this out with, then you can just create yourself some files, then use them as if they were block devices:

# mkfile 128m /export/stuff/disk1
# mkfile 128m /export/stuff/disk2
# zpool create testpool mirror /export/stuff/disk1 /export/stuff/disk2
# zpool status testpool
pool: testpool
state: ONLINE
scrub: none requested
config:

NAME STATE READ WRITE CKSUM
testpool ONLINE 0 0 0
mirror ONLINE 0 0 0
/export/stuff/disk1 ONLINE 0 0 0
/export/stuff/disk2 ONLINE 0 0 0

errors: No known data errors

The cool thing about this procedure is that you can create as many virtual disks as you like and then test ZFS's features such as data integrity, self-healing, hot spares, RAID-Z and RAID-Z2 etc. without having to find any free disks.

When creating a pool for production data, think about redundancy. There are three basic properties to storage: availability, performance and space. And it's a good idea to prioritize them in that order: Make sure you have redundancy (mirroring, RAID-Z, RAID-Z2) so ZFS can self-heal data when stuff goes wrong at the hardware level. Then decide how much performance you want. Generally, mirroring is faster and more flexible than RAID-Z/Z2, especially if the pool is degraded and ZFS needs to reconstruct data. Space is the cheapest of all three, so don't be greedy and try to give priority to the other two. Richard Elling has some great recommendations on RAID, space and MTTDL. Roch has also posted a great article on mirroring vs. RAID-Z.

4. The power to give

Once you have set up your basic pool, you can already access your new ZFS file system: Your pool has been automatically mounted for you in the root directory. If you followed the examples above, then you can just cd to /mypool and start using ZFS!

But there's more: Creating additional ZFS file systems that use your pool's resources is very easy, just say something like:

zfs create mypool/home
zfs create mypool/home/johndoe
zfs create mypool/home/janedoe

Each of these commands only takes seconds to complete and every time you will get a full new file system, already set up and mounted for you to start using it immediately. Notice that you can manage your ZFS filesystems hierarchically as seen above. Use pools to manage storage properties at the hardware level, use filesystems to present storage to your users and applications. Filesystems have properties (compression, quotas, reservations, etc.) that you can easily administer using zfs set and that are inherited across the hierarchy. Check out Chris Gerhard's blog on more thoughts about file system organization.

5. Snapshot early, snapshot often

ZFS snapshots are quick, easy and cheap. Much cheaper than the horrible experience when you realize that you just deleted a very important file that hasn't been backed up yet! So, use snapshots whenever you can. If you think about whether to snapshot or not, just do it. I recently spent only about $220 on two 320 GB USB disks for my home server to expand my pool with. At these prices, the time you spend thinking about whether to snapshot or not may be more worth than just buying more disk.

Again, Chris has some wisdom on this topic in his ZFS snapshot massacre blog entry. He once had over 60000 snapshots and he's snapshotting filesystems by the minute! Since snapshots in ZFS “just work” and since they only take up the space that actually changes between snapshots, there's really no reason to not doing snapshots all the time. Maybe once per minute is a little bit exaggerated, but once a week, once per day or once an hour per active filesystem is definitely good advice.

Instead of time based snapshotting, Chris came up with the idea to snapshot a file system shared with Samba whenever the Samba user logs in!

6. See the Synergy

ZFS by itself is very powerful. But the full beauty of it can be unleashed by combining ZFS with other great Solaris 10 features. Here are some examples:

  • Tim Foster has written a great SMF service that will snapshot your ZFS filesystems on a regular basis. It's fully automatic, configurable and integrated with SMF in a beautiful way.

  • ZFS can create block devices, too. They are called zvols. Since Nevada build 54, they are fully integrated into the Solaris iSCSI infrastructure. See Ben Rockwood's blog entry on the beauty of iSCSI with ZFS.

  • A couple of people are now elevating this concept even further: Take two Thumpers, create big zvols inside them, export them through iSCSI and mirror over them with ZFS on a server. You'll get a huge, distributed storage subsystem that can be easily exported and imported on a regular network. A poor man's SAN and a powerful shared storage for future HA clusters thanks to ZFS, iSCSI and Thumper! Jörg Möllenkamp is taking this concept a bit further by thinking about ZFS, iSCSI, Thumper and SAM-FS.

  • Check out some cool Sun StorageTek Availability Suite and ZFS demos here.

  • ZFS and boot support is still in the works, but if you're brave, you can try it out with the newer Solaris Nevada distributions on x64 systems. Think about the possibilities together with Solaris Live Upgrade! Create a new boot environment in seconds while not needing to find or dedicate a new partition, thanks to snapshots, while saving most of the needed disk space!

And that's only the beginning. As ZFS becomes more and more adopted, we'll see many more creative uses of ZFS with other Solaris 10 technologies and other OSes.

7. Beam me up, ZFS!

One of the most amazing features of ZFS is zfs send/receive. zfs send will turn a ZFS filesystem into a bitstream that you can save to a file, pipe through bzip2 for compression or send through ssh to a distant server for archiving or for remote replication through the corresponding zfs receive command. It also supports incremental sending and receiving out of subsequent snapshots through the -i modifier.

This is a powerful feature with a lot of uses:

  • Create your Solaris zone as a ZFS filesystem, complete with applications, configuration, automation scripts, users etc., zfs send | bzip2 >zone_archive.zfs.bz2 it for later use. Then, unpack and create hundreds of cloned zones out of this master copy.

  • Easily migrate ZFS filesystems between pools on the same machine or on distant machines (through ssh) with zfs send/receive.

  • Create a crontab entry that takes a snapshot every minute, then zfs send -i it over ssh to a second machine where it is piped into zfs receive. Tadah! You'll get free, finely-grained, online remote replication of your precious data.

  • Easily create efficient full or incremental backups of home directories (each in their own ZFS filesystems) through ZFS send. Again, you can compress them and treat them like you would, say, treat a tar archive.

See? It is easy, isn't it? I hope this guide helps you find your way around the world of ZFS. If you want more, drop by the OpenSolaris ZFS Community, we have a mailing list/forum where bright and friendly people hang out that will be glad to help you.

"7 Easy Tips for ZFS Starters" has been brought to you by Constantin's Blooog.
This entry was created on 2007-09-06 11:20:15.0 PST and is associated with the following tags:

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20070816 Thursday August 16, 2007

ZFS Snapshot Replication Script

One of the OpenSolaris' ZFS filesystem's greatest features are its snapshots. You can easily create a snapshot by saying zfs create pool/filesystem@snapshot and then replicate that snapshot by saying something like zfs send pool/filesystem@snapshot | zfs receive newpool/some_other_filesystem. So far, so great.

Now let's say you have a nice pool and have been creating snapshots on a regular basis. After a few months, you decide to remodel your pool layout or migrate some of your filesystems over to a new pool for whatever reason. Then, you're facing a lot of those zfs send and receive commands. Especially, if you're like Chris and do snapshots on a per-minute basis. That's why the ZFS community is now waiting for 6421958: A zfs send -r option.

I had to migrate quite a few filesystems and many snapshots (thanks to Tim's excellent ZFS Snapshot SMF Service) lately when I set up a new pool strategy for my home server so I wrote myself a script to do the replication job. Since it may take some time for the send -r feature to be implemented, I turned it into a more generic utility.

Disclaimer: Please be advised that this script has only been tested a couple of times and it is provided to you completely on an "as-is" basis. Please have a look at the script to understand how it works and try it out on some non-risky pools and filesystems before you do real stuff with it. Run a backup before using this script and don't shoot me if something goes wrong.

Ok, what can this script do for you? First of all, check out its -h flag to see what options it provides:

# zfs-replicate -h
usage: zfs-replicate [-h] [-F ] [-n] [-s] [-v]
         [-m [-c "FMRI|pattern[ FMRI|pattern]...]" ]
         source dest

where source and dest is a ZFS filesystem, snapshot or volume.

Options:
-h: Print this help.
-F: Force a rollback of the destination filesystem to the most recent
    snapshot before replicating a snapshot. This is equivalent to the -F
    option of zfs receive.
-n: Don't actually replicate anything, just print what would be done.
    This will only print the next step but nothing dependent on that step
    since it won't actually be executed. For instance, -ns will print the
    snapshot command but not print the subsequent send/receive command as it
    depends on the snapshot actually being taken.
-s: After sending existing snapshots, make a final one and replicate it as well.
    This option requires that the source be a filesystem and not a snapshot.
-m: After sending all snapshots, migrate the source to the dest filesystem by
    unmounting the source filesystem and changing the new filesystem's
    mountpoint to that of the source one. This option includes -s.
-c: A space delimited list of SMF services in quotes to be temporarily disabled
    before unmounting the source, then re-enable after changing the mountpoint
    of the destination. Requires -m.
-v: Be verbose.

Great, let's try it out. Here's a pool with some data and some snapshots as well as another, empty pool:


# zfs list -r piscina
NAME                            USED  AVAIL  REFER  MOUNTPOINT
piscina                         384M  87.6M    19K  /piscina
piscina/ficheros                384M  87.6M   384M  /piscina/ficheros
piscina/ficheros@instantanea1    17K      -   128M  -
piscina/ficheros@instantanea2    17K      -   256M  -
piscina/ficheros@instantanea3      0      -   384M  -
# zfs list -r lago
NAME   USED  AVAIL  REFER  MOUNTPOINT
lago   105K   472M    18K  /lago

Now, let's copy the ficheros filesystem along with all its snapshots in one go:


# zfs-replicate -v piscina/ficheros lago
Sending piscina/ficheros@instantanea1 to lago.
Sending piscina/ficheros@instantanea2 to lago.
(incremental to piscina/ficheros@instantanea1.)
Sending piscina/ficheros@instantanea3 to lago.
(incremental to piscina/ficheros@instantanea2.)
# zfs list -r lago
NAME                         USED  AVAIL  REFER  MOUNTPOINT
lago                         384M  87.6M    20K  /lago
lago/ficheros                384M  87.6M   384M  /lago/ficheros
lago/ficheros@instantanea1    17K      -   128M  -
lago/ficheros@instantanea2    17K      -   256M  -
lago/ficheros@instantanea3      0      -   384M  -

It works. And it automatically used incremental snapshots as well to save space, too!

If we now add another snapshot to our original pool piscina and then run zfs-replicate again, it will skip already replicated snapshots and just copy those that are additional:


# zfs snapshot piscina/ficheros@instantanea4 
# zfs-replicate -v piscina/ficheros lago
Sending piscina/ficheros@instantanea4 to lago.
(incremental to piscina/ficheros@instantanea3.)
# zfs list -r lago
NAME                         USED  AVAIL  REFER  MOUNTPOINT
lago                         384M  87.6M    20K  /lago
lago/ficheros                384M  87.6M   384M  /lago/ficheros
lago/ficheros@instantanea1    17K      -   128M  -
lago/ficheros@instantanea2    17K      -   256M  -
lago/ficheros@instantanea3      0      -   384M  -
lago/ficheros@instantanea4      0      -   384M  -

This is useful because you can now run this script on regularly basis to have one pool automatically backed up to another pool. In fact, the -s option will first make sure all existing snapshots are copied over, then create a new snapshot for you and copy that one over as well, all in one command.

Sometimes, the destination filesystem gets touched, or otherwise acted upon and then zfs receive to it will no longer work. In that case, you can use the -F switch which will force a rollback of the destination filesystem to its latest snapshot and then you'll be back in business.

Finally, another scenario is file system migration: You have a filesystem in one pool and want to migrate it with all it's snapshots to another pool, with minimal downtime. This can be done using the -m option: First copy all existing snapshots while the source file system is still live, then unmount it, create a final snapshot, copy that one over to the destination file system as well, set the destination filesystem's mountpoint to be the same as the source filesystem's one and remount the destination file system. (Please note that the script might appear frozen when unmounting while it's waiting for some open files to be closed, etc.).

If you're worried about some daemons depending on your filesystem's availability (like Samba), you can use the -c option to provide their names. zfs-replicate will then bring down the matching SMF services right before unmounting and restart them automatically after re-mounting the migrated filesystem. Again, you might need to wait until the SMF service is really down (Read: The last Samba connection has closed).

I hope this script is useful to you and again, I assume you know what you're doing and do some testing before using it in production. I'm sure there are still some bugs and shortcomings so please send me email to constantin (dot) gonzalez (at) sun (dot) com or leave a comment and I'll try to make the script better for you.

Many thanks to Chris Gerhard, whose backup script was an inspiration for me in hacking together this utility. Also, many thanks to Tim Foster for some code-review and initial feedback (Sorry, I haven't managed to implement some locking yet...). Let me know when you're in Munich and you'll get some well-deserved beer!

"ZFS Snapshot Replication Script" has been brought to you by Constantin's Blooog.
This entry was created on 2007-08-16 13:41:02.0 PST and is associated with the following tags:

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Constantin's Blooog by Constantin Gonzalez is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License.
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