Mailinglist Archive: opensuse (818 mails)

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Re: [opensuse] Reiserfs (was ext4 vs btrfs)
On 7/18/2012 4:31 PM, John Andersen wrote:
On 7/18/2012 11:40 AM, Brian K. White wrote:
Triple power supplies means you can unplug one power cord at a time to
transfer to a long extension cord from the other rack, then transfer
from the extension cord to the pdu in the rack when you get there,
without ever losing power along the way

Do you have any clue how dangerous that is?

Let me see, ham license when I was 11 (which means '81, which means no cb-like licenses that didn't require electronics, radio theory, and code that they have now), EE in college, ... yes. None at all.

The 2 or 3 (depending on how you want to count) possible things I'm guessing you're thinking of aren't an issue.

Redundant ps's are meant to be both disconnected and reconnected, while live and under load, at any unknown time, from the same circuit or different circuits (ie possibly out of phase, possibly different hz, possibly square vs sine, util vs gen vs ups, reconnected too fast before caps drained, etc), either from the power cord or by ejecting the entire ps. That is not merely something like abuse that good ones can tolerate, but the explicit designed purpose of them all in the first place, even cheap-o's.

A robust engineer doesn't invite problems unnecessarily of course no matter how much everything is supposed to be ok, which is why of course I didn't say I do that every day either.

At the same time, another part of being robust is you are actually supposed to exercise things and procedures once in a while to ensure they work and are available to you when you may need some time. Things that should work, but are normally ill advised for some reason, should be done on purpose once in a while or else you never can rely on the procedure working on that bad day when you really need it.

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