My LiveJournal blog name - valhenson - was the last major holdover from my old name, Val Henson. I got a new Social Security card, passport, and driver's license with my new name several months ago, but migrating my blog? That's hard! Or something. I finally got around to moving to a brand-spanking-new blog at WordPress:

Valerie Aurora's blog

Update your RSS reader with the above if you still want to read my blog - I won't be republishing my posts to my new blog on this LiveJournal blog.

If you're aware of any other current instances of "Val Henson" or "Valerie Henson," let me know! I obviously can't change my name on historical documents, like research papers or interviews, but if it's vaguely real-time-ish, I'd like to update it.

One web page I'm going to keep as Val Henson for historical reasons is my Val Henson is a Man joke. Several of the pages on my web site were created after the fact as vehicles for amusing pictures or graphics I had lying around. In this case, my friend Dana Sibera created a pretty damn cool picture of me with a full beard and I had to do something with it.



It's doubly wild now that I have such short hair.

ZFS now has data deduplication - with the right configuration options for safety and performance in a compare-by-hash based storage system. From Jeff Bonwick's ZFS deduplication blog entry:

Given the ability to detect hash collisions as described above, it is possible to use much weaker (but faster) hash functions in combination with the 'verify' option to provide faster dedup. ZFS offers this option for the fletcher4 checksum, which is quite fast:

zfs set dedup=fletcher4,verify tank

The tradeoff is that unlike SHA256, fletcher4 is not a pseudo-random hash function, and therefore cannot be trusted not to collide. It is therefore only suitable for dedup when combined with the 'verify' option, which detects and resolves hash collisions. On systems with a very high data ingest rate of largely duplicate data, this may provide better overall performance than a secure hash without collision verification.

What I like is (1) the user chooses the hash function based on their security and performance needs, (2) the system can optionally check for hash collisions, and (3) the ZFS storage pool design makes it easy to migrate data to a new hash function if necessary. ZFS is the first deduplicating storage system I know of with these features. (Do let me know if there are others out there!)

For my money, the Bay bridge can stay closed. I couldn't believe what a difference it made when the Bay bridge was closed over Labor Day weekend. My crappy, noisy, stressful SOMA neighborhood became quiet and pedestrian-friendly. Birds sang. Property values would skyrocket. Even just closing half the lanes would make a huge difference.

Anyway, to do my teensy-tiny part in making this a possibility, I just want to remind people that you can work around the Bay bridge closure even if your ultimate destination isn't on public transit. Just take BART across and get a Zipcar the rest of the way.

Today I was bicycling back from the Golden Gate Bridge and got trapped in a surprise Columbus Day parade in North Beach. This happens to me a lot - I am out minding my own business somewhere in SF and suddenly I am surrounded by thousands of strangely dressed, probably drunk people who are in between me and my home. I have been surprised by Bay to Breakers, Pride, Folsom Street Fair, SantaCon, a zombie flash crowd, the Blue Angels, and now a Columbus Day parade. Did you know there was a Columbus Day parade in San Francisco? Neither did most of the people watching it.

Is there an RSS feed somewhere out there for "things happening in San Francisco involving several thousand people that might screw up your day OR even be fun to attend?" 'Cause I would subscribe to it.

My latest LWN article is out:

Featherstitch: Killing fsync() softly

Subscriber-only for another week. My last article is now free to read for all:

Log-structured file systems: There's one in every SSD

And I'm not sure I posted the one before that:

POSIX v. reality: A position on O_PONIES

I just posted the union mounts (now called writable overlays) design doc to LKML and fsdevel:

[RFC] Union mounts/writable overlays design

Along with it is a new release, featuring:

* Rebase against 2.6.31
* pivot_root() and rename() support
* jffs2 support (thanks to Felix Fietkau)

I booted this one on my laptop with a root file system as a writable overlay, and got all the way up to the (text) login prompt with only a couple of complaints about missing chmod() and link() support. Yeah!

The patches that need to be rewritten have useful comments in their commit messages, and the fixes are described in detail in the design doc. So if you want to jump in and do a little bit of development, you can do so even if you're not a VFS expert (which is most of us).

As usual, all the good stuff linked to from here:

Writable overlays (a.k.a. union mounts)

Have fun!

My laptop has rivets in it:



My cat knocked it off the desk about a year ago and broke one of the hinges. It spent most of the following year wrapped up in gobs of electrical tape with an assortment of picture hanging parts as braces. Last weekend, my boyfriend basically splinted the broken hinge with a combination of sheet metal, double-sided adhesive tape, and rivets. I think the new hinge is actually smoother and less floppy than the original Dell XPS M1330 hinge.

I only work for Red Hat part-time; the rest of the time I write and consult on file systems. I'm experimenting with a new consulting service: on-site training classes on the file system topic of your choice. The goal is not a canned PowerPoint lecture, but a combination of in-depth personal instruction and an opportunity to pick my brain on whatever file systems problem is keeping you and your engineers awake at night. If you've seen me speak at a conference, it will look a lot like that plus an extra hour of question and answer time.

For the test run, I'm offering an in-person two-hour class, unlimited attendance, Bay area location only, at the discounted rate of $2500 for the first three customers to set a date. If the experiment is a success, I'll offer more classes at a substantially higher rate. :)

If you're interested, talk to someone who can approve training expenses at your company, and then email:

info@vaaconsulting.com

I just read Charlie Stross's rant on reducing his household's carbon footprint. Summary: He and his wife can live a life of monastic discomfort, wearing moldy scratchy 10-year-old bamboo fiber jumpsuits and shivering in their flat - or, they can cut out one transatlantic flight per year and achieve the equivalent carbon footprint reduction.

I did a similar analysis back around 2007 or so and had the same result: I've got a relatively trim carbon footprint compared to your average first-worlder, except for the air travel that turns it into a bloated planet-eating monster too extreme to fall under the delicate term "footprint." Like Charlie, I am too practical, too technophilic, and too hopeful to accept that the only hope of saving the planet is to regress to third world living standards (fucking eco-ascetics!). I decided that I would only make changes that made my life better, not worse - e.g., living in a walkable urban center (downtown Portland, now SF). But the air travel was a stumper. I liked traveling, and flying around the world for conferences is a vital component of saving the world through open source. Isn't it? Isn't it?

Two things happened that made me re-evaluate my air travel philosophy. One, I started a file systems consulting business and didn't have a lot of spare cash to spend on fripperies. Two, I hurt my back and sitting became massively uncomfortable (still recovering from that one). So I cut down on the flying around the world to Linux conferences involuntarily.

You know what I discovered? I LOVE not flying around the world for Linux conferences. I love taking only a few flights a year. I love flying mostly in the same time zone (yay, West coast). I love having the energy to travel for fun because I'm not all dragged out by the conference circuit. I love hanging out with my friends who live in the same city instead of missing out on all the parties because I'm in fucking Venezuela instead.

Save the planet. Burn your frequent flyer card.

I was rummaging through my old pictures and found this one of the sign at the security checkpoint at Lihue airport in Kauai:



Damn, I forgot and left my spear in my purse!