On Jul 21, 2009, at 2:24 PM, Bob Friesenhahn wrote:
On Tue, 21 Jul 2009, Richard Elling wrote:
With wear leveling and zfs you would probably discover that the
drive suddenly starts to wear out all at once once it reaches the
end of its lifetime. Unless drive ages are carefully staggered,
or different types of drives are intentionally used, it might be
that data redundancy does not help. Poof!
Eh? Would you care to share how you calculate this?
It assumes that the devices are manufactured perfectly with quite
uniform properties and very well designed wear leveling which
exposes all cells to the same degree of wear. Perfection
theroretically results in Poof!
Bad assumption. Not only are semiconductor processes quite
variable, performance depends on environmental conditions like
temperature.
But to put this in perspective, you would have to *delete* 20 GBytes of
data a day on a ZFS file system for 5 years (according to Intel) to
reach
the expected endurance. I don't know many people who delete that
much data continuously (I suspect that the satellite data vendors might
in their staging servers... not exactly a market for SSDs)
-- richard
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