Automatic means for spinning down disks available?

Gary Kline kline at
Thu Apr 12 01:22:09 UTC 2007

On Wed, Apr 11, 2007 at 04:14:33PM -0700, Chuck Swiger wrote:
> On Apr 11, 2007, at 3:32 PM, Gary Kline wrote:
> >	Some things to consider (besides powering -down or -off drives)
> >	are battery backup system.  Don't most UPS systems isolate your
> >	servers from the wall-socket?
> The better grade of UPSes do exactly that-- they provide "galvanic  
> isolation" by using an isolation transformer which has the primary  
> and secondary windings completely separated, and ensuring in the  
> design that you don't connect the service neutral line to the output  
> or load's neutral line.  The load can thus either be floating or tied  
> to the local building ground.  This type of design is known as  
> "double-conversion" because they always feed the input AC line  
> through the rectifier & DC inverter, using more power but providing  
> better PFC and can provide the load with an AC frequency which is  
> different than the input AC frequency (ie, they can provide 60Hz  
> output from 50Hz input, or vice versa).

	Years ago I spent a lot of money for a top notch surge
	protector.  It still protects everything to this day; and very
	well.  Now and then I'll find my LAN down, DNS too, obviously, 
	because of a surge of one sort or another.  The power here 
	(Seattle) is pretty good -- well, except for wind storms {koff}.
	But I'm way past due for having the sort of higher quality 
	UPS that  you're taking about.  It would be wired to a pipe struck
	in the  earth.  Floating_ground just doesn't cut it.  Any models
	you'd recommend?  How much system installation is required?
	I'm CAT-5A cabled.  Software, no problem; anything else is.

> Cheaper UPSes, which include almost all consumer-grade models from  
> APC, Tripplite, etc run in "line interactive mode", which involves a  
> self-tapping or ferro-resonant transformer, can adjust the voltage up  
> or down within limits, but they do not perform PFC and cannot provide  
> frequency conversion, and they pass the neutral line from AC line to  
> load without isolation, thus passing common-mode noise through.  This  
> design is lighter and requires fewer components (an isolation  
> transformer is heavier), and does not keep the DC section and  
> inverter always under full load, so are somewhat more efficient, but  
> cannot deal with frequency drift or significant voltage changes.

	Understand, thanks, Chuck.  Here (where rubber-meets-pavement
	is where *not* to cheap out).  

> >  At what level do hard drives have identical circuitry so that  
> >they can be software lower-voltaged?
> The boards within a drive family might be identical (WD200BB/WD400BB/ 
> WD800BB/etc), but they don't deal with under-voltages at all well--  

	{{ this is what i was afraid of.... }}

> you'll either pull excessive current through the servo and spindle  
> motor windings, or perhaps the drive will fail to spin up entirely.   
> The spindle motors are designed to spin at the calibrated speed and  

	So, pragmatically, a drive is either going full-throttle or
	it's OFF.  ...Hm.  

> won't spin at slower speeds.

	Somewhere, prhaps at the Gnome shutdown GUI (dialogue?)
	it reads: Off, Changed-user, Idle, Power-Off, Reboot, 
	or whatever.  Flame from Gnome/KDE folks to /dev/null, please.
	I'm guessing the "Idle" is for the laptops.   YEs/no?

	Something else to consider here is how much power do the newer
	40-60, 200-300GB drives suck up?  I don't think the drain is
	much compared to, say, 3 CRT television sets drowning on 
	several hours/day.  Still, let's SWAG that there are 25-30
	million of us nerd/geek types running at least one computer.
	That adds up.

> >	*Except for consumer __cost__*, why don't all boxes have builtin
> >	batteries like laptop?  ...There are lots of things to consider.
> Cost is the primary reason why boxes don't have built-in batteries.   
> People flinch away from paying for real RAID systems which include  
> battery-backup for the drives...

	Well, then I'm definitively part of the problem; suspect that 
	most of my kinsfolk are too.  aNy idea how mmuch of this could be
	solved by software?  Maybe when a machine turns itself off at
	03:30, it write a state-file.  When it reboots  {either by magic
	timer or by actually crawling around down there and toggling 
	switches }, presto, you have everything just the way you left it.

	puts("Feedback, world?");


> -- 
> -Chuck

  Gary Kline  kline at  Public Service Unix

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