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DragonFly kernel List (threaded) for 2004-09
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Re: vinum?

From: "Greg 'groggy' Lehey" <grog@xxxxxxxxx>
Date: Tue, 14 Sep 2004 10:00:16 +0930

On Monday, 13 September 2004 at  8:45:30 -0700, Matthew Dillon wrote:
>     If you want *real* RAID, you want to use an external raid with a SCSI
>     port.  Second choice would be to use a real raid controller.  Third
>     choice would be to use a software solution.

Well, they're all *real* RAID :-)  But yes, putting it in a BSD kernel
is a bit of a hack.  Volume management is a different issue.

>     Vinum is a rather fragile piece of software, it would not be my
>     first choice despite all the fine work done on it.

The run-time components of Vinum are surprisingly (to me, anyway)
robust.  It's the configuration stuff that needs replacement, as
mentioned in a previous message.

>     As far as Geom goes... well, I really dislike the idea of having
>     to implement complex drivers in the kernel.  I have been slowly
>     cleaning up our IO infrastructure to allow IO devices to be
>     properly stacked (our disk layer, for example, is now properly
>     stacked), but ultimately I think the real win here will be to
>     form a streaming protocol that could run over a TCP socket to
>     govern the I/O (not necessarily NAS).  Then one would be able to
>     build drivers to run in userland and/or on remote machines.  The
>     only real latency issue is, as always, with READ ops, but a
>     kernel supported data block cache at the block device level
>     would mostly solve that issue.

FWIW, I'm currently planning to write a userland callout for the file
system so that I can prototype file systems in userland.  If anybody's
interested in following up on this one, please contact me.  It
obviously doesn't belong on this thread.

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