On Thu, 21 Jul 2005, Matthias Kurz wrote:
I don't think so, because of my understanding on physics, the stress to
material is higher when the temperature is changing, than at a constant
level. spinning up an down would mean that during backup the temperature
of the drives are rising to go down afterwards.
The problem in electronics is in uneven expansion rates of the
semiconductor chips vs the much larger carrier and interconnection wires.
Drives themselves face stresses across the platters, but these are far
outweighed by bearing wear and airstream wear issues - various makers have
done studies and recommend various balances, but if the drives are going
to remain unused for more than 12 hours, then it's a safe bet to spin them
down.
Thermal calibration issues are well understood and most of those issues
were solved years ago. I only ever see them occur in infant mortality or
end-of-life situations for drives which are not physically abused or
carried around a lot.
Well, six of the seven drives would be unused for one week, when i
understood your concept. When they are unnecessarily running they waste
a lot of power and generate a lot of unnecssary heat.
Older arrays are usually worse: as an example our first 10TB array draws
about 5kW and the newer 13TB array draws about 900W. The older one has no
"green" features too.
I don't think that this is measurable in mid size data center.
Depends on how much equipment you extend your opinion ;-)
It is when there are a lot of disk arrays.
No, i do not really want to argue too much. It was just a stray idea. And
when there would be a prebuilt, working solution - one that probably takes
your arguments into account and "heats up" the disk(s), before it fully
uses it - it would not be a bad thing. And when every bacula user in the
whole world would use it... ;-)
Nexsan Atabeast raid controllers have this feature built in. You can also
achieve it by enabling power saving features on individual drives.
Spindown is becoming more and more of an issue in datacentres,
particularly with increasing power consumption due to increased server
density.
I'll ask one simple question: Do you keep your drives long enough that any
degradation caused by power cycling vs continuous operation becomes
obvious? If it does in normal equipment lifetime (3-5 years in most
buinesses) then you need to change supplier.
AB
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