druck  wrote:
> On 17/12/2020 01:47, bob prohaska wrote:
>> As evolution plays out it may well favor SSD.
>
> That's done and dusted,
>
>> For now HDDs seem to
>> be developing the same handicaps as SSDs. I think HDDs still win
>> on write cycles and power consumption. Not sure how they compare for
>> practical life span. Life span is a function of overprovisioning for
>> SSD, if SSD costs keep dropping they might win on both counts.
>> Last I checked SSDs were a little worse for power consumption, but
>> that was months ago and I don't know where the trend is going.
>
> The problem I see ahead for SSDs is the move to QLC (4 bits per cell),
> at the cheaper end, which has an order of magnitude less life than TLC
> (3 bits per cell).
>
> Although this was said for the move from SLC (1 bit per cell) and MLC (2
> bits per cell) to TLC, but that has provided pretty rock solid over the
> last 6 or 7 years, with the use of advanced controllers, wear levelling
> an over provisioning.
>

It might be useful to re-frame the issue in terms of failure mode. If a
machine fails gracefully, how long it's going to last becomes much less
worrisome. If a storage device gives warning that it's running out of
write capacity I might not be afraid of QLC vs lower-density options.

If it just goes all bricklike, with no warning at all, it's a lot less
attractive. Just the ability to test how much over-provisioning remains
available would be a big help. SMART keeps some track of deterioration
in mechanical drives, does it exist for SSDs?

Thanks for reading,

bob prohaska

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