Re: Mirror server?

Hi all,

[Dave Hudson <dave@humbug.demon.co.uk> writes:]
> The implementation I was thinking of would connect to all of the
> devices/partitions/files that we'd like to store data on and provide a
> mechanism whereby these would be seen as one logical device. The server
> would advertise a port that to all intents and purposes would appear to be
> any other block device.

I think its important to decide what the end goal is when combining
multiple physical devices into a single logical device, as this greatly
affects the way the server is implemented and how data is organized.
Some goals are:

        1. data replication

        2. performance

        3. the ability to extend logical data storage by adding
        new physical devices

Note that the goals aren't independent of each other. For example,
replicating data in some fashion may affect performance.

You also have to be careful that you don't create more problems than
you solve. For example, one decides that to increase the effective
disk transfer rate by stripeing two disks, but discovers that the
average rotational latency just increased (assuming the disks aren't
spindle locked) or that the I/O bus is a bottle neck, etc.

> I know there'd be issues with handling fails

There also needs to be system-management level software that, among
other things, does the following:

        1) builds up and tears down stripe/mirror sets.

        2) brings new disk members on-line

        3) sets policies

> ... but I'd think that VSTa must
> be a superb environment to tinker with this sort of code.

I agree. The ability to put this stuff into a server along with VSTa's
ability to connect servers together is much better than, for example,
having to link a new pseudo driver into the kernel that has to jump
through a number of hoops to get thing working properly.

                                        Mike Larson
Received on Fri May 13 08:13:49 1994