Re: [9fans] Changelogs & Patches?

[erik quanstrom <quanstro@quanstro.net>]

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

since these arguments rely heavily on the meme that
	software raid == bad
i have a hard time signing on.  i believe i'm repeating
myself by saying that afik, there is no such thing as pure
hardware raid; that is, there is no hardware that does
all of what raid level n does in hardware.  even if it's
an embedded processor, it's all software raid.  perhaps
there's an xor engine to speed things along.

the other part of the argument — the "write hole"
depends on two things that i don't think are universal
a) zfs' demand for transactional storage b) a particular
raid implentation.

fancy raid cards often have battery-backed ram and thus
from the pov of the host, writes are atomic.  i don't have
any nda that let me see the firmware for a variety of raid
devices, but i find it hard to believe that all raid vendors
rewrite the entire stripe whever the write is smaller than
the stripe size and all could rewrite the data before the
parity.

> 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.

more people use windows than use plan 9.  should
i therefore conclude that my use of plan 9 is illogical?
http://en.wikipedia.org/wiki/Appeal_to_the_majority

why do you think that mpi has anything to do with
a plan 9 infastructure?

> May be your numbers are wrong, may be your usage
> patterns are different. Who knows.

a single cpu on ec2 costs $150/month.  my 6 personal
machines don't suck down that much juice.

the machines i have largely cost less than $500.  so
that's like $14/month.  that doesn't change the equation
much.

- erik