[Spread-users] Wackamole IP takeover time

[Theo Schlossnagle]

On Saturday, July 13, 2002, at 07:04 PM, Min Lu wrote:
> Thanks. That's what I was looking for "10-20 milliseconds to switch the
> virtual IPs".
> Is this recorded from lab test or is it an educated guess?

Educated guess.  But I have seen take over times of less than then in 
practice when a service fails (instead of a machine).  As Yair said, 
when a machine fails, the Spread daemon membership must take place 
before the notifications will reach wackamole... So this could take 
several seconds -- but it could be tuned to be much tighter than this.

> On another note, does anyone know if  there is any open source
> disk mirror driver like DRDB for Solaris?  Someone must have
> done it already since it is a popular platform. WE don't like Sun's
> commercial equivalent that costs $$$$.

I personally _really_ like the commercial volume manager for Solaris.  I 
assume you are speaking of the Veritas Volume Manager.  I think the 
Veritas suite of software storage facilities is unparalleled.  I have 
not seen a volume manager and filesystem combo that even approaches its 
quality for standard UNIX environments -- free or commercial.

I am unaware of any open source volume management applications for 
Solaris.  If you are just talking about a kernel driver to mirror a disk 
and do fail over, I would image that would be trivial to implement -- 
but it seems to only provide a little whereas something like VxVM + VxFS 
provides everything you could ever want.

My two cents. :-D

Like most things.  If you have an application that _requires_ the sort 
of availability that can only be provided by such software tools, 
chances are the price is not that substantial in that picture.  On a 
parallel, Sun Cluster does tons of stuff that wackamole will simply 
never do -- if you truly _need_ Sun Cluster, chances are you can afford 
it.

--
Theo Schlossnagle
Principal Consultant
OmniTI Computer Consulting, Inc. -- http://www.omniti.com/
Phone:  +1 301 776 6376       Fax:  +1 410 880 4879
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