[Info-vax] Marketing ideas for VSI ?

[Arne Vajhøj]

On 12/15/2018 10:33 AM, Kerry Main wrote:
>> From: Info-vax <info-vax-bounces at rbnsn.com> On Behalf Of Bill Gunshannon via Info-vax
>> Sent: December 14, 2018 9:45 PM
>> If it were me I would be pushing the concept of long distance clusters.
>> Machines geographically distant so as to survive major natural and man made
>> upheavals.  The biggest drawback I remember from when I was more up to
>> date on this was network latency and that has really become less of an issue
>> today.
> 
> Actually network latency is primarily based on speed of light (hops also),
> and this has not changed since the speed of light was originally calculated.

Increasing speed of light would solve a lot of problems in widely
distributed configs.

But unless we can pull a LAN cable through a worm hole then I think
we are out of luck.

:-)

> Other factors to consider for long distance clusters and how far apart the
> can be is the R/W ration of the application This is because active-active
> clusters with load balancing across both sites requires  synch replication.
> A heavy write app will mean you will likely need to have sites closer
> together than the standard 100km rule of thumb that is usually stated in the
> context of long distance clusters. This causes performance issues if a heavy
> write bogs down the app while it is waiting for writes to occur at both
> sites before the update is considered complete at either site.

It is not just the latency itself aka waiting for response.

With TCP and waiting for ACK's and having a fixed window size it
can also hurt throughput.

Depending on context some chose options like consider a transaction
committed if it is on the plates locally and sent aka on the wire
to one or more remote sites.

Arne