Re: Larry Ellison comments on Microsoft's benchmark

On Fri, 07 Jul 2000 04:08:47 GMT, Ivana Humpalot wrote:

>"Blair Kenneth Adamache" <adamache_at_ca.ibm.com> wrote:
>>
>> You can cross mount disks with shared nothing (also called drive
>> mapping). Only one node owns the disk at any time. If the owner node
>> fails, the mutual takeover node gets the IP of the failing node, and
>> takes over the disk.
>
>Thank you for the info and the link to IBM documentation. From
>what I understand, MSCS clusters are limited to 2 servers per
>cluster. So if you have 12 machines you have 6 independent
>clusters. Isn't this still 6 times less reliable than Oracle
>Parallel Server?

Let's use some "real" fake numbers. Let's pretend that each machine has a failure rate of 10%. This is awfully high, but it's a nice, round number. ;-)

One machine: 10% failure rate.

Twelve machines: 100% - ((100% - 10%)^12) = 71.75% failure rate.

1 2-way mutual-failure takeover cluster: 10% ^ 2 = 1% failure rate.

6 2-way mutual-failure takeover clusters: 100% - ((100% - 1%) ^ 6) = 5.85% failure rate.

12-way mutual-failure takeover cluster: 10% ^ 12 = 10^(-10)% failure rate.

"6 times" is a misnomer. But even with a huge overstatement of the failure rates, it can become reasonable fairly quickly.

NOTE!!! I did not take reliability engineering courses - only engineering statistics. Which means that while I'm not completely unqualified in reliability analysis, it's close. :-) Received on Fri Jul 07 2000 - 00:00:00 CDT