Re: [9fans] Changelogs & Patches?

["Roman V. Shaposhnik" <rvs@sun.com>]

On Mon, 2009-01-26 at 08:53 -0500, erik quanstrom wrote:
> > It depends on the vdev configuration. You can do simple mirroring
> > or you can do RAID-Z (which is more or less RAID-5 done properly).
>
> "raid5 done properly"?  could you back up this claim?

Yes. See here for details:
   http://blogs.sun.com/bonwick/entry/raid_z

> > > does this depend on the amount of i/o one does on the data or does
> > > zfs scrub at a minimum rate anyway.  if it does, that would be expensive.
> >
> > You can do resilvering (fixing the data that is known to be
> > bad) or scrubbing (verifying and fixing *all* the data). You
> > also can configure things so that bad blocks either trigger
> > or don't automatic resilvering. Does this answer your question?
>
> no.  not at all.

Then, please, restate it.

> if you're serious about using ec2, one of the
> costs you need to control is your b/w usage.  you're going to
> notice overly-aggressive scrubbing in your mothly bill.

Only if you asked for that to happen. Its all under your control.
You may decide to never ever do scrubbing.

> > The scariest takeaway from the conference was: with the economy
> > the way it is physical on-site datacenters are becoming a
> > luxury for all but the most wealthy companies. Thus whether
> > we like it or not virtual data centers are here to stay.
>
> if the numbers i came up with for coraid are correct, it would would cost
> coraid about 50x more to use ec2.  that is, if we can run plan 9
> at all.

You may think what you want, but obviously quite a few existing small to
mid-size companies disagree. Including a couple of labs with MPI apps
now running on EC2. May be your numbers are wrong, may be your usage
patterns are different. Who knows.

Thanks,
Roman.