On Sat, Jun 6, 2020 at 9:57 AM antlists <antli...@youngman.org.uk> wrote: > > Oh - the other thing - if it's PMR and you're copying files onto it, > expect a puke! That thing on WD Reds going PMR, I copied most of that on > to the linux raid mailing list and the general feeling I get is "PMR is > bad". >
You're mixing up PMR/SMR there. PMR=CMR=the way things have been for the last few decades. SMR is the new shingled technology. There is nothing wrong with it per se, but it is NOT a drop-in substitute for all applications. It works best if it is host-managed with a filesystem or application that was engineered specifically to use it. If you tried to swap a hard drive with a tape drive you'd have terrible results 99% of the time, but that doesn't make tape drives a bad thing. They just aren't drop-in substitutes for hard drives and you need to use them with appropriate applications. One of the problems with drive-managed SMR is that it can seem to be ok when you're just doing light duty access, and then when one of your other drives fails and you're doing a zfs resilver the SMR drive starts performing an order of magnitude or more worse and you find yourself painted in to a corner. -- Rich
