Slow ZFS resilver performance - would this be a reason to go back to HW RAID?

[alpha754293]

@ThisMightBeAFish

So now that we know that we only get 66.66%, is that really worth the downsides of RAIDZ2 over mirror? Just to get 16% more storage efficiency, we are willing to have the write performance of a single disk instead of four?

For a 8-drive wide raidz2/RAID6 - I get 75% of the raw capacity.

(n-2)*min(drive capacity) = (8 - 2) * (6 TB) = 6 * 8 TB = 48 TB.

If I were using mirror/RAID1, it would be n/2*min(drive capacity) = 8/2 * 6 TB = 4 * 6 TB = 24 TB.

(And the 6 TB drives are currently being replaced with 12 TB drives, which means that the vdev raw capacity will double, as will the usable capacity, which will incrementally add 48 TB to my bulk storage pool, overall.)

So even WITH the loss in capacity due to the two parity drives, I LITERALLY have TWICE the amount of usable capacity by going with raidz2/RAID6 than I do if I were to have gone with using mirrors instead.

You can literally wiki the math for the various RAID levels or use any of the online RAID capacity calculators to prove this out. (cf. https://www.qnap.com/en-us/selector/raid-selector?gad_source=1&gclid=Cj0KCQjw05i4BhDiARIsAB_2wfAl-3vl7IQ_Sg0q-1M1u4LjCUuOFAMSZGvWGELSFvOOoALgzdaZGCkaApFyEALw_wcB)