Re: Periodic refresh (or rwrite?) of data on an SSD (was: Re: Recommended SSDs and 4-bay internal dock)
On Fri, 13 Jan 2023, at 15:33, rhkramer@gmail.com wrote:
> I've read some of that article, or, I guess, really the abstract and the
> section labeled "Content" on that page:
>
> https://www.ibm.com/support/pages/potential-ssd-data-loss-after-extended-shutdown
Is there a longer article? I have the impression that the Abstract & Content on that
page is all there is.
There seems to me to be some ambiguity about the way they write about "40C"
which - I presume - is ambient temperature. Are they saying that these drives are
rated to be used in temperatures not exceeding 40 degrees C (ie that if the temp
is even higher the situation is likely (far?) worse than what's described here?
That is, should the sentence "The JEDEC spec for Enterprise SSD drives requires
that the drives retain data for a minimum of 3 months at 40C."
be read as
"The JEDEC spec for Enterprise SSD drives requires that the drives retain data
for a minimum of 3 months at /temperatures of up to but not exceeding/ 40C."
because this is also ambiguous
"This means that after 3 months of a system being powered off in an environment
that is at 40C or less, there is a potential of data loss ..."
Either you can read that as implying the "40C or less" is part of the cause of data
loss, or that it means
"that after 3 months of a system being powered off in an environment that is
/working as designed/ at 40C or less, there is a potential of data loss"
that is, that it's the lack of power that's the cause, not the temperature.
>From a chilly UK standpoint, 40 degrees C seems very high. I wonder if data
retention is better or worse at - say - ambient temps of eg 15-20 degrees?
I wonder how much worse home-user SSDs are than these Enterprise-rated
ones.
The whole issue makes me wonder if, say, I should plan on having several
SSDs for each set of backup data (I mean separately from the common-
sense approach of having more than one copy of anything anyway). Then
every n weeks, delete the data from the least-recently written drive and
copy a fresh copy (from the most recently written drive) onto that one, &
verify that every file copied has the same hash as its original. (I suspect
I'd want to keep lists of file hashes anyway, as a way of detecting when
any backups start to go bad.)
I'm not sure that that was clear. What I mean is that if I intended to keep
a backup of a driveful of data, I might choose to have, say, this week's
copy, last week's, and the week before. So apart from the original disk
I'd have 3 other backup drives.
Then for each of those there'd be two other drives in use, so 9 in all...
--
Jeremy Nicoll - my opinions are my own.
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