Raid 1+0

[Jon Radel]

On 4/19/16 2:44 PM, Valeri Galtsev wrote:
> My opinion that your conclusion that the drives having the same MTBF 
> (or similar lifespans) are likely to die simultaneously contradicts my 
> understanding of probability theory (or statistics basics). People 
> life expectancy in some country is 75 years. Likelyhood that two 
> _given_ people will die at age 40 is negligible. Even twin brothers 
> are unlikely to die during the same week or Month. This one is between 
> fundamental assumptions statistics is based on. Just my humble 
> opinion. Valeri
You're confusing presence of correlation with a layman's "really, really 
likely."

Of course the probability that two people of the same age will die in 
the same month is higher than the probability that two randomly selected 
people will die in the same month.  Likelihood of death is not constant 
throughout life.  Frankly I take the actuaries that suggest my insurance 
company up my life insurance premiums every 5 years waaaaaay more 
seriously than you.

If you assume away all the interesting bits, your conclusions get pretty 
useless.

Actually, people study this stuff.  See, for example:

http://biomedgerontology.oxfordjournals.org/content/53A/6/M441.full.pdf

--Jon Radel
jon at radel.com

-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 3890 bytes
Desc: S/MIME Cryptographic Signature
URL: <http://lists.freebsd.org/pipermail/freebsd-questions/attachments/20160419/13e16d75/attachment.bin>