----- Original Message -----
From: Pieckiel, Kevin A <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, January 12, 2000 7:35 AM
Subject: Redundant fileservers
> Hi all. Please comment on the following:
>
> We are wanting to replace our current method of backing up our fileserver
> (which is via a tape drive) by making our fileserver redundant. That is,
> another machine that will be a live mirror of the "in-use" fileserver. If
> anything on the active fileserver fails, we'd like things to fail-over to
> the redunant server so that the users won't see a single hiccup.
> Our fileservers run RHL 6.1, BTW, with the latest stable kernel (2.2.14 at
> present).
>
> Where do I begin? Is this possible?
>
Sure, there are several options for doing this. Actually though, from your
description, you don't REALLY want just a mirror of the hard drive, you want
a HA (high availability) cluster. Some references:
1. The Linux HA HOWTO:
http://metalab.unc.edu/pub/Linux/ALPHA/linux-ha/High-Availability-HOWTO.html
#toc4
Mainly theory, but has several good links for current projects and tells
you how to join the Linux-HA mailing list.
2. Heartbeat: http://www.henge.com/~alanr/ha/comm/#Heartbeat
A failry robust and popular freeware cluster monitoring software
solution.
> I've seen much support for raid devices in mirroring drives in the same
> computer, but no Linux support for mirroring drives to another computer.
> Are there better alternatives than the idea presented here?
>
See above. One option presented in the HA HOWTO is to use a win tailed SCSI
system to actually reverse the concept and let two CPU's access the same
SCSI RAID array. RAID does the work of keeping the data safe, and the
multiple CPU setup handles failover conditions.
> Our monetary goals for this are aimed here --> all free software, or very
> low cost; hardware for a standard fileserver (like we already have) is
> already available less a hard drive, so we look to purchase ony a matching
> hard drive for that which is in our current fileserver.
>
Again, it sounds to me like what you're asking for is a HA cluster, and
building one from existing parts is a low cost (although higher manual
labor) option.
One caveat: None of this will free you from tape backups. Drive array
failure or mirror corruption can always still occur, and tape backup is the
cheapest insurance on the block. You'll notice in all the HA literature that
it's still recommended that tape backups be continued as the last defense
against data loss.
HTH,
Brad 'GreyBear' Davis
Ronin Coder/Bithead at Large
-----------------------------------------------
'Don't crush that dwarf, hand
me the pliers!'
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