On 18/05/2021 17:05, Phillip Susi wrote:
Wols Lists writes:
When rebuilding a mirror (of any sort), one block written requires ONE
block read. When rebuilding a parity array, one block written requires
one STRIPE read.
Again, we're in agreement here. What you keep ignoring is the fact that
both of these take the same amount of time, provided that you are IO bound.
And if you've got spinning rust, that's unlikely to be true. I can't
speak for SATA, but on PATA I've personally experienced the exact
opposite. Doubling the load on the interface absolutely DEMOLISHED
throughput, turning what should have been a five-minute job into a
several-hours job.
And if you've got many drives in your stripe, who's to say that won't
overwhelm the i/o bandwidth. Your reads could be 50% or less of full
speed, because there isn't the back end capacity to pass them on.
Cheers,
Wol
