> MTBF of a RAID-0 system (or dual cpu/memory where one unit CAN
> NOT continue
> without the other) will always be lower than a single drive unless the
> standard deviation (they never quote SD) of the MTBF is zero.
Well, if you take duty-cycle into account, which MTBF calculations do, you
will actually get higher MTBF for RAID 0, simply because the main failure is
the servo actuator, and when it is only being used for half the time...MTBF
will increase.
> The reality for MTBF of a RAID-0 will lie in between.
But that means it doesn't change compared to a single drive...
> Cummalative failure rate is a much more useful figure for us and
> for a small
> number of fairly reliable inter-dependant devices this is nearly
> an additive
> figure - but not quite.
That I completely disagree with. It is absolutely NOT additive. In fact,
as I pointed out above, you may get HIGHER reliability by using RAID 0
simply because of duty cycle and the common failure mode, both of which are
a very important part of MTBF.
> Seagate reckon about 3.41% (flat-line model) will fail during the first 5
> years of use (assuming you only use it for 2400 hours a year [6
> 1/2 hours a
> day]) :
>
>
If you read that article you referenced, when they talk about multiple
disks, they are talking about multiple PLATTERS in a single disk, not
drives, so you can't derive the numbers you did for multiple drives from
that article. No where in that article did they discuss multiple drives.
