I searched each to find the section where 2x was
discussed. What I found was interesting. First, there are really only 2 positions here:
Micron's and Red Hat's. Supermicro copies Micron's positon paragraph word for
word. Not surprising considering that they are advertising a Supermicro / Micron
solution.
FWIW, at Cephalocon another vendor made a similar claim during a talk.
* Failure rates are averages, not minima. Some drives will always fail sooner
* Firmware and other design flaws can result in much higher rates of failure or insidious
UREs that can result in partial data unavailability or loss
* Latent soft failures may not be detected until a deep scrub succeeds, which could be
weeks later
* In a distributed system, there are up/down/failure scenarios where the location of even
one good / canonical / latest copy of data is unclear, especially when drive or HBA cache
is in play.
* One of these is a power failure. Sure PDU / PSU redundancy helps, but stuff happens,
like a DC underprovisioning amps, so that a spike in user traffic results in the whole row
going down :-x Various unpleasant things can happen.
I was championing R3 even pre-Ceph when I was using ZFS or HBA RAID. As others have
written, as drives get larger the time to fill them with replica data increases, as does
the chance of overlapping failures. I’ve experieneced R2 overlapping failures more than
once, with and before Ceph.
My sense has been that not many people run R2 for data they care about, and as has been
written recently 2,2 EC is safer with the same raw:usable ratio. I’ve figured that
vendors make R2 statements like these as a selling point to assert lower TCO. My first
response is often “How much would it cost you directly, and indirectly in terms of user /
customer goodwill, to loose data?”.
Personally, this looks like marketing BS to me. SSD
shops want to sell SSDs, but because of the cost difference they have to convince buyers
that their products are competitive.
^this. I’m watching the QLC arena with interest for the potential to narrow the CapEx
gap. Durability has been one concern, though I’m seeing newer products claiming that eg.
ZNS improves that. It also seems that there are something like what, *4* separate EDSFF /
ruler form factors, I really want to embrace those eg. for object clusters, but I’m VERY
wary of the longevity of competing standards and any single-source for chassies or drives.
Our products cost twice as much, but LOOK you only
need 2/3 as many, and you get all these other benefits (performance). Plus, if you
replace everything in 2 or 3 years anyway, then you won't have to worry about them
failing.
Refresh timelines. You’re funny ;) Every time, every single time, that I’ve worked in an
organization that claims a 3 (or 5, or whatever) hardware refresh cycle, it hasn’t
happened. When you start getting close, the capex doesn’t materialize, or the opex cost
of DC hands and operational oversight. “How do you know that the drives will start
failing or getting slower? Let’s revisit this in 6 months”. Etc.