Vertical Scaling

[Amin Rais]

I read that Vertical Scaling reduces the Reability ... how it can ?
Is replacing processor for example from
1 Ghz to 2 Ghz is also vertical scaling ?
or Vertical scaling just mean by "adding"
not "replacing" processor and memory..
I know that by adding new processor then
the reability is reduced a bit..
because we have more probability of fail
caused by new added processor (if one
fail, then all of them are fail).
Thx,
Amin

[Rufus BugleWeed]

These rule of thumbs you state are not 100%.
If your airplane has two motors and one fails
you still have the other.
Going from a 1.2GHz to a 2.0Ghz is vertical
scaling.

[Gus Dur]

Yeah I don't understand also very well..
Vertical:
Achieved by adding capacity (memory, CPUs, etc.) to existing servers.
Requires few to no changes to the architecture of a system.
Increases: Capacity, Manageability
Decreases: Reliability, Availability
How can it reduce reliability and availability,
in my opinion, it remains the same...
Gus Dur

[Bill william]

these are the disadvantages of vertical scaling when it is compared to horizontal scaling

Originally posted by Gus Dur:

How can it reduce reliability and availability,
in my opinion, it remains the same...
Gus Dur

[Sanjay Raghavan]

My $0.02
In that statement, the author does not really imply that VS will reduce Reliability / Scalability, perhaps the way to read it would be that VS will have little / no impact on Reliability and Availability, as compared with HS.
VS, as has been pointed out is achieved by adding processors / memory ...as opposed to HS, where new servers are added.
If you have just changed your server from a 2 processor m/c to a 4 processor m/c, how does that change availability / reliability? In multi-processor systems, the underlying OS is intelligent enough to spread its processing load amongst the processors. However if the disk array crashes, what difference will it make whether there were 2 or 4 processors? None. The m/c is down. Does both reliability and availability threats still exist even after VS.
As opposed to VS, in HS, new machines are added. You also either have specialized applications that can manage load or your software supports some kind of clustering and redundacy. In this example, if one server fails, the redundancy machanism will kick off and the system will continue to be available. Thus HS actually enhances the Reliability / Availability of a system.
HTH.