>>> Would the hot spare be in case I lose 2 drives at once? Isn't that >>> extraordinarily unlikely? >> >> Not really. One fails and you don't notice for a while, or it takes a while >> to >> recover from it. Then a second one fails. You're up queer street. > > I like to do RAID6 now because I've been burned by this. The hot spare > did work and automatically start rebuilding, but another drive failed > during the rebuild process. Not that RAID6 will help if three drives > fail, but hey.
This article references the same scenario: http://blog.open-e.com/why-a-hot-spare-hard-disk-is-a-bad-idea/ "Based on our long years of experience we have learned that during a RAID rebuild the probability of an additional drive failure is quite high – a rebuild is stressful on the existing drives." Instead, how about a 6-drive RAID 10 array with no hot spare? My guess is this would mean much greater fault-tolerance both overall and during the rebuild process (once a new drive is swapped in). That would mean not only potentially increased uptime but decreased monitoring responsibility. - Grant
