[OpenAFS] Summary of recommended configuration options from the workshop

Derrick Brashear shadow@gmail.com
Mon, 26 May 2008 21:38:35 -0400

On Mon, May 26, 2008 at 6:38 PM, Robert Banz <rob@nofocus.org> wrote:
>> From the conference:
>> Why Derrick doesn't use fastrestart
>> 1) You have to have something parse logfiles and salvage it
>> 2) If you're running an inode fileserver, every time you salvage you crawl
>> all of the inodes. You salvage 10 volumes, you're going through 10*<number
>> of inodes>
> I agree with Derek's analysis --

Dude, when did warlord comment?

>that yes, in the event you'd really have to
> salvage, you could salvage a lot.
> However, in my experience, salvaging has only been necessary in the face of
> a hard system crash -- basically, problems with data written to the
> filesystem out-of-order from what AFS thinks it should be, etc. If you're
> unlucky to be running in an environment where your storage is unstable, or
> your filesystem doesn't guarantee (or close to it) ordered writes, you've
> got other problems. Though, I'd say it's very reasonable to salvage after a
> hard crash -- perhaps that's a job for an init script, or the administrator
> that was investigating the cause of the failure.

I want self-healing. Also, fileservers do themselves occasionally crash.

> In most situations where I was running into that required a fileserver
> restart with prejudice (kill -9) -- things like thread lockups -- I've never
> had to salvage, and fastrestart is a lifesaver when you have fileservers
> with a good deal of data.  Customers don't enjoy 30+ minutes of outage.

Me either. Even ignoring demand attach, namei plus well-tuned salvager
is fast, though, so luckily i don't actually care.