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Date:      23 Jan 1999 22:57:29 +1100
From:      "John Saunders" <john.saunders@nlc.net.au>
To:        freebsd-isp@FreeBSD.ORG
Subject:   Re: ccd and vinum
Message-ID:  <19990123115729.25303.qmail@nhj.nlc.net.au>
In-Reply-To: <19990123115446.A26886@freebie.lemis.com>

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Greg Lehey <grog@lemis.com> wrote:
> ccd is on its way out, not in.

As long as it hangs around long enough for me to figure out how to
configure vinum (and to compile a RELENG_3 kernel without errors
when vinum is included) I will be happy.

>> Granted if a disk fails you'll have some down-time as you swap in
>> new drives a rebuild the mirrors, but at least it's minimal and you
>> have much less chance of loosing data than say from restoring from
>> tape.
> In the cases I've seen, you need to reboot the machine, reconfigure
> ccd, recover manually, reconfigure ccd, possibly reboot, and then
> you're back up and running again.

I have a system where I ran remove the failed drive and be back running
in an un-mirror configuration pretty quickly. However once I source
a replacement drive there is about 40 minutes downtime to sync the
new disk up. Rebuild in background would be a real time saver.

>>   1) Are any of you ISP's using it, and it it stable?
> I don't use it, but I believe it's relatively stable.

Yes on 2 servers. At a remote POP I have one machine running modems,
mail, news cache and http cache, using ccd to mirror two 4.5GB drives.
Another machine is a http cache with a couple of drives with a 128
sector strip. I can get a sustained 7.5MB/sec to Quantum Fireball
IDE drives. Reliability isn't an issue, it just runs.

>>   2) I assume that the root partition can't be ccd.  Correct? and
> Correct.

Can it be with vinum? That would be interesting. Currently I have to
remember to manually sync up the root filesystems if I change them.

I looked into it some time back. It is probably possible to have a
ccd root filesystem if you hack a kernel to do the equivalent of
ccdconfig and then get it to mount the ccd device as root. Although
it would require substantial code hacking.

> On the other hand, vinum does the right thing: if a drive fails, it
> will carry on running, and you can rebuild the volumes on line.  Take
> a look at http://www.lemis.com/vinum.html.

Sounds really good, if I can get the $%^$& thing to compile I will be
happy. :-)

Cheers.
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