ZFS at Aberystwyth

I just arrived back from Aberystwyth, where at the invitation of the Campus Ambassador I was giving a talk on ZFS to the students and staff.

The thing about giving ZFS presentations and demonstrations is that they are really good fun. You don't have to overplay the point with gimics however fun they are. Or at least you don't if your audience is technical. For a start having disks fail gracefully (even if this is due to a hammer) is not new. The Solaris volume manager could cope with that. O.k it did not have double parity raid but again that is not the really cool part of ZFS. That is just cool.

The coolest part of ZFS is the ability to recover from silent data corruption. The dd over one side of a mirror demo or one disk in a RAIDZ or even 2 disks in RAIDZ2 and have ZFS survive and recover. That is really cool.

The other things that caused a noticeable drawing of breath from the audience were rollback and data sharing via snapshot and clone.

Faced with those things it is hard to underestimate the power of having those snapshots always available under the .zfs directory and the beautiful simplicity of the administration.

For an added bonus I ran the whole presentation and demo while booted from the OpenSolaris live cd. Demonstrating that if you want to play with this stuff you don't actually need to install Solaris. The only problem I had was that I could not get the nvidia driver to accept that the projector was capable of more than 640x520.

I really enjoyed the session and from the comments afterwards so did many others.

Comments:

I have trouble with the nVidia driver as well. My monitor does not support DDC version 2, only version 1, and this seems to cause the driver problems. I only get 640x480 unless I create my own xorg.conf with a "modes" line specifying the resolutions, and some "modeline" lines specifying the timing data - which it should be getting via DDC!

Posted by andrewk8 on May 08, 2008 at 01:52 PM BST #

I filed bug: 6699742 nvidia-settings should allow you to choose any resolution for an external monitor/projector

for this.

Posted by Chris Gerhard on May 12, 2008 at 04:42 AM BST #

One more idea for ZFS silent data corruption recovery demo - creating ufs filesystem over single-disk pool with couple of filesystems in it - one with default settings, another one with ditto blocks enabled, and a copy of the same file in each one. I did it during Sun Tech Days in SPB...

Posted by Victor Latushkin on May 19, 2008 at 10:46 AM BST #

Hmm, last time I put UFS on a zvol I had to increase the default stack size to prevent a stack overflow.

Posted by Chris Gerhard on May 19, 2008 at 11:08 AM BST #

Idea is not to put UFS on a zvol. It is something like this:

mkfile 500m /file

zpool create pool /file

zfs create -0 copies=3 pool/ditto

cp <50m file> /pool

cp <50m file> /pool/ditto

digest -a md5 /pool/file

digest -a md5 /pool/ditto/file

zfs list

zpool export pool

zpool import pool

lofiadm -a /file

echo y | newfs /dev/rlofi/1

zpool status -v

digest /pool/file

zpool status -v

digest -a md5 /pool/ditto/file

zpool status -v

zpool clear

digest -a md5 /pool/ditto/file

zpool status -v

Posted by Victor Latushkin on May 21, 2008 at 05:09 PM BST #

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This is the old blog of Chris Gerhard. It has mostly moved to http://chrisgerhard.wordpress.com

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