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Can turning a RAID off an on be damaging?


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#1 sev_on_sr

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Posted 20 November 2012 - 12:59 PM

My friend uses 2 RAIDS for his Autodesk Flame set-up. As far as I know, it's not hosting any files outside of a local network, or being used overnight. Yet he says that it's better for the whole system to leave them running all the time, which seems crazy since the fans are so loud and it's a waste of energy. Any insight would much appreciated.

-sev

#2 FastMHz

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Posted 11 December 2012 - 01:08 PM

Hard drives prefer to stay on and spinning. Thermal expansion and contraction is highly destructive over time. In short, power cycles break things.

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#3 [ETA]MrSpadge

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Posted 11 December 2012 - 02:32 PM

It's true that on-/off cycles are the most damaging part of normal operation for an HDD. However, I think there's more to this discussion.

First: HDDs are designed to take a lot of on-/off cycles. Typically 50k, if I remember correctly. At 2 cycles per day (switching off after work) that's a good 68 years.

Second: while start/stop are the most stressful operations for an HDD, they don't last very long. Normally spinning the platters also causes some wear, which adds up over time. By not turning the HDDs off one exposes them to longer runtimes.

Third: keeping the HDDs spinning requires energy. And if you say the fans are really loud then they also consume a few W each. I don't know your exact numbers and about how many HDDs we're talking about here, but in Germany each W being drawn 24/7 typically costs about 2/year (US prices will be much lower). If I assume 2 arrays with 4 HDDs each, assuming 5.4k rpm with high platter counts (best for bulk storage) and ~5 W per drive, that's 40 W for the drives alone. Now add 1 fan with 2.5 W for each array and we're looking at 45 W, i.e. 90/year running costs. If the arrays were being powered down half of that time we'd save about 45/year. Currently a 2 TB HDD here costs a bit over 80, 3 TB for 120. So the savings could buy 1 TB worth of additionally failed HDDs each year (at the current prices, these are slowly dropping over time).

Personally I'd don't think we're in the "just leave it on" age pf PCs any more, as electricity starts to really cost. Most people don't notice these costs as they're hidden in some yearly fee which is huge anyway. However, switching an HDDs on and off frequently is one of the surest ways to kill it.

MrS

#4 FastMHz

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Posted 11 December 2012 - 03:00 PM

I do agree that it's a trade off of electric cost vs power cycles. A bunch of "green" drives will of course draw less wattage than a bunch of 7200 rpm or 10,000 rpm drives.

That said, personally I prefer data integrity over a few bucks a month on my electric bill and leave the 5400rpm drives in my NAS spinning 24/7. The thought of a power cycle is painful! UPSs are your friend, because a good surge will kill them just as fast.

I have some really old hard drives around....and the oldest survivors are the ones that have low power cycles.

I do power down my workstations at night.

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