…8TB drives in an mdadm raid take a lllllloooooooonnnnnggggg time to sync, Raid 1 allows for one drive failure, so let's say you have to replace a failing drive within that mirror, during that sync it stops because the good drive has failed. Bye, Bye data, the same is for a Raid 5 allows for 1 drive failure within the array, whilst the raid is rebuilding 1 of the 2 good drives dies, bye, bye data.
Why such a big downer on RAID? As I said, I am well aware of what RAID means and of course level 5 was specifically developed to cope with hardware failure of a single drive and if a second fails before the first has been replaced and the array all sync'd, then obviously data will be lost. But what's the alternative? No RAID means single failure and data IS lost, are you trying to suggest that is a better solution.
As I said, this is for a media server and if the data is lost, that's just some missing TV time. Not gonna cause WW3 to break out and it doesn't warrant the significant cost of duplicating the entire storage space for a full backup which is also not required for individual file reversion reasons. The files will be stored and then not changed. So I only need to prevent total data loss from HDD failure and the chances of 2 drives failing at the same time are remote. Not impossible I grant you, but highly unlikely. Certainly a far smaller chance than that of a single drive failure.
So, I do wish to take advantage of what RAID 5 offers, i.e. a good chance to avoid loss of data due to the failure of a single drive. I was using RAID 5 very effectively 30 years ago and I cannot believe it is less effective now than it was then.
I've similarly been using the command line in *nix for 30 years now so do not presume to think I am ignorant and incapable of doing so now. However, for speed and simplicity, I would prefer to be able to administer this server using the web GUI as much as possible, but first priority is to be able to achieve the functionality I require and if that requires using the CLI, then so be it.
Having said that, the server is not yet complete and I have no prior experience of OMV, nor mdadm on any flavour of *nix, hence my questions here.
Why is RAID 5 based on 8 TB drives such a bad idea. Does array recovery take more than twice as long as for 4 TB drives? Or is there some capacity threshold above which recovery time increases exponentially? Just trying to understand the reasons for your criticism of a large RAID 5 array in mdadm.
Since there's no need to duplicate the entire data store as a full backup (and certainly want to avoid the significant expense of that), but you opine that RAID 5 is such a bad idea, what is your suggestion?