Re: Spare disk could not sleep / standby

[Brad Campbell <brad@wasp.net.au>]

Gordon Henderson wrote:
> 
> I'm in the middle of building up a new home server - looking at RAID-5 or
> 6 and 2.6.x, so maybe it's time to look at all this again, but it sounds
> like the auto superblock update might thwart it all now...

Nah... As far as I can tell, 20ms after the last write, the auto superblock update will write the 
array as clean. You can then spin the disks down as you normally would after a delay. It's just like 
a normal write. There is an overhead I guess, where prior to the next write it's going to mark the 
superblocks as dirty. I wonder in your case if this would spin up *all* the disks at once, or do a 
staged spin up, given it's going to touch all the disks "at the same time"?

I have my Raid-6 with ext3 and a commit time of 30s. With a idle system, it really stays idle. 
Nothing touches the disks. If I wanted to spin them down I could do that.

The thing I *love* about this feature, is when I do something totally stupid and panic the box, 90% 
of the time I don't need a resync as the array was marked clean after the last write. Thanks Neil!

Just for yuk's, here are a couple of photos of my latest Frankenstein. 3TB of Raid-6 in a Midi-Tower 
case. Had to re-wire the PSU internally to export an extra 12v rail to an appropriate place however.

I have been beating Raid-6 senseless for the last week now and doing horrid things to the hardware. 
I'm now completely confident in its stability and ready to use it for production. Thanks HPA!

http://www.wasp.net.au/~brad/nas/nas-front.jpg
http://www.wasp.net.au/~brad/nas/nas-psu.jpg
http://www.wasp.net.au/~brad/nas/nas-rear.jpg
http://www.wasp.net.au/~brad/nas/nas-side.jpg


Regards,
Brad
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