[Linux-HA] some newbie questions

[Miles Fidelman]

Hi Folks,

I'm about to migrate from a dedicated RH9 server (mostly email, list 
serving, web serving) to a couple of new machines that I'll be 
deploying  in a colocation arrangement - with a lot more control over 
configuration.

My current box is pretty basic - using RAID-1 and nightly backups to 
provide a measure of reliability.  I'm planning on taking the 
opportunity of deploying new machines to build a more robust site.

As I explore the options, I'm running into more questions than answers, 
so I'd very much appreciate any guidance that anyone can offer on the 
following (and on any other topics you think are relevant).

My basic idea is to run two boxes - one as primary, one configured for 
automatic failover.  Beyond that I'm thinking of running a few virtual 
servers for staging/experimentation purposes.

The hardware I have available are fairly high-end i86 boxes, 2Gig each, 
with 4 400Meg SATA drives in each, and dual gigE nics.

On to questions:

1. DRBD seems like the way to go to mirror data between the boxes, but 
what about mirroring data on each box as well, so that a disk failure 
doesn't lead to having only one copy of data?  Does it make sense to run 
DRBD over md software mirroring?  How bad would the performance hits 
be?  Is there a better approach?  Can anybody suggest an optimal 
configuration?

2. How much worse does it get if I introduce virtual servers?  Any 
suggestions re. vserver vs. Xen (and Xen 2 vs. Xen 3)?

3. What about adding a volume manager into the mix?  LVM vs. EVMS?

4.  Any suggestions regarding adding an off-site mirror (i.e., adding 
network mirroring to the mix)?  Does something like CODA make sense?

5.  Now what I'd REALLY  like to do is run on FreeBSD rather than 
Linux.  Are any of these capabilities available in the BSD world?

Thanks very much, in advance, for any suggestions.

Miles Fidelman