Lifespan of RAID-0 vs Single Hard Disk Theoretically

Assume the lifespan of hard disks are independent and identically distributed.

Let the probability of lifespan of a hard disk be P(t)
Let the CDF of P(t) be C(t)

CDF of minimum of 2 i.i.d. random variable is 1-(1-C(t))^2
And then differentiate the above w.r.t. t, we have
PDF of RAID-0 is 2*(1-C(t))*P(t)

So, for any distribution of lifespan P(t), the RAID-0 comparing to single hard disk is always 2*(1-C(t)) times more likely to fail.

—-

To illustrate the difference, let further assume P(t) is Normal distribution with mean = 5 years and s.d. = 1 years

single_vs_raid0

single_vs_raid0_2

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s