[plug] Fax & Voicemail Random Thought...

[Craig Ringer]

> 2. After power problems (eg, pushing the off switch instead of the CD
> eject switch, which are only about an inch apart), files, other than tmp
> files, are sometimes converted or whatever, to the status or whatever, of
> 6 (I remember the number, but not what is done, that achieves the
> number), during the subsequent fsck. The files have included /dev and /var
> files. I do not know what damage has been done, but, it appears that files
> do get damaged (apart from the ones that at the same time, get the wrong
> lengths and things, that also need "fixing").

A journalling filesystem will fix that, its caused by data half-written 
to disk when the power was lost.

>>The computer won't be damaged by power loss.
> 
> Given the damage that has been done to appliances that we have owned, and
> the short lifetimes of light globes in this house, due to the unstable
> electricity supply

Yeah, that'd be dealt with by power conditioning (for the PCs) provided 
by a UPS. Power loss won't hurt them though, its _bad_ power that can.

> It is also probably why
> the stepper motor on my 10MB HDD has to be kickstarted, most of the time,
> on one of my computers.
Aah, a 10mb hdd. Cool. I've got a 5mb SCSI one (full-height) 'round here
somewhere, taken from an _old_ mac. Still works on the SCSI RAID 
controller in the Athlon server too :-)
More seriously, that drive may be old enough to be physically damaged by 
power failure (head crashes). I had no idea you'd be using hardware 
quite _that_ old.

>>So really, there's no problem with leaving a PC on 24/7, and many have a 
>>BIOS option to auto-reboot on power loss too, so your machine comes 
>>straight back up after a power failure.
> 
> Looking after our PC's, and protecting them (as much as possible from a
> wonky power supply), and turning them off when not needed, to avoid power 
> problems, is why we still have hard drives that operate without any
> problems, that are over 10 years old.

Fair enough. I guess in part my priorities just don't go that far toward 
PC lifetime - six to eight years is good, I'd be pretty annoyed at 5 
years though. But hey, if you're willing to put in the effort and care 
to keep them running, thats fair enough.

>>Of course for anything truly critical (hideously expensive, mission 
>>critical for work, or whatever) a proper UPS with battery pass-through 
>>and good power conditioning is a must.
> 
> To students, everything on the hard drive (that is related to study, not
> blue pictures :), is critical, or, should be. More than one PhD student
> has lost their thesis, just before handing it in, due to computer
> failures.

Backup *whack* backup *whack* backup *whack* ....
;-/
I was meaning more stuff that needs to be up 24/7 and where daily 
backups just aren't good enough.

> In Armadale, a computer with anything of value on the hard drive,
> warrants a good UPS. It's like travelling in a car wearing a seat belt -
> it's a matter of survival (and, works, for most cases).

Makes sense. I hope it is a _good_ UPS though - many "desktop UPS" units 
sold now are AFAIK not "proper" UPSs - they switch from mains to battery 
if they detect a current drop on the mains, but they don't do proper 
battery pass-through for clean power conditioning etc.

-- 
Craig Ringer
GPG Key Fingerprint: AF1C ABFE 7E64 E9C8 FC27  C16E D3CE CDC0 0E93 380D
	-- if it ain't broke, add features 'till it is. (or:)
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