From mboxrd@z Thu Jan  1 00:00:00 1970
From: erik quanstrom <quanstro@quanstro.net>
Date: Mon, 11 Apr 2011 06:38:53 -0400
To: 9fans@9fans.net
Message-ID: <7701de2dc841cea75d598f543d9c24f7@ladd.quanstro.net>
In-Reply-To: <77bc353d-543a-4c00-9239-3cac84b0e9e3@bl1g2000vbb.googlegroups.co>
References: <77bc353d-543a-4c00-9239-3cac84b0e9e3@bl1g2000vbb.googlegroups.co>
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Subject: Re: [9fans] stream alternative?
Topicbox-Message-UUID: cf07fa68-ead6-11e9-9d60-3106f5b1d025

> Also, in a previous question (http://groups.google.com/group/
> comp.os.plan9/browse_thread/thread/771294cf1d34c337) it was stated
> that streams are no longer used. So what's the present mechanism that
> replaces streams?

there isn't one.  you can't dynamically reconfigure i/o paths in plan 9.

however, since everything's a file server, one can construct fairly
arbitrary chains of devices.  (and given the bread/bwrite calls in the
kernel, it can be zero-copy.)

zB: aoe(3) presents basic block devices.  partitions aren't supported.
however, sdaoe(3) which is a lightly specialized version of sdloop(3)
turns one into a sd(3) device, which does support partitions.  sdloop
(only in 9atom) can do the same thing for anything that looks like a
regular file.

so imagine that i for some bizarre reason i wanted to run raid50
locally on aoe targets.  i could run a fictive sdraid5 on a fictive
set of sdraid1 devices which in turn were built from sdaoe on top
of aoe.  so you'd have

	sdraid5* <-> sdraid1* <-> sdaoe <-> aoe <-> ether

maybe that looks like streams to you, even if it's not dynamically
reconfigurable.

personally, that looks more like Device in ken's file server
to me.

- erik