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  #1  
Old 09-05-2009, 12:17 PM
Sophie Sophie is offline
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Power outage during backup

My city has power outages every few weeks, specially in summer. What happens (to either source disk or backup disk) if a SuperDuper backup is running and power is lost?

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Old 09-05-2009, 02:21 PM
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Of course, as you must expect, the drives can be damaged. It's best to use an Uninterruptible Power Supply with your computer and drive(s).
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Old 09-05-2009, 02:31 PM
Sophie Sophie is offline
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So far Leopard has recovered fine from random power failures, presumably thanks to journalling. My disks are all standard MacOS Extended (Journaled).

Could the source disk get damaged too? Any worse than just power failure in Leopard?
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Old 09-05-2009, 04:44 PM
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Whether its caused by a power outage or other reasons, there's always a risk of data corruption or other damage with any abnormal system shutdown. Not having a UPS battery backup under conditions like you've mentioned is unwise unless you're willing to continue risking problems with every power outage that crashes your computer. You're already wiser than many people by having a data backup and having a power backup would be smart, too.

Last edited by sjk; 09-05-2009 at 04:48 PM.
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Old 09-05-2009, 06:35 PM
Sophie Sophie is offline
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Thanks SJK.

At the prices for a UPS rated long enough to let unaccompanied backup jobs complete, times the number of Macs to protect, plus the aesthetics challenges, it becomes a question of risk. I would certainly not be putting a UPS on every Mac if it was just OSX recovering its file system.

That's why I'd really like to understand if the damage risks are higher during backup jobs than with just OSX doing its normal file system recovery. If I stand a real risk to lose both source and backup disks during a SuperDuper backup job in a form that would not be OSX recoverable then the UPS becomes mandatory ... hopefully a more informed smart decision :-)
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Old 09-06-2009, 02:48 AM
TMay TMay is offline
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Sophie

I'm sure when Dave gets a minute from putting out fires, he'll comment, but if I understand the specific question you are asking, I think the answer is "no." I see no reason why the source volume would be at any more risk during a power failure when it is performing a backup job than when it is performing any of myriad other tasks.

I have found the recent Apple systems to be quite resiliant in power failure crash situations, but there is always the risk. But I don't think a backup running at the time of the failure increases (nor does it diminish) the risk.

The backup, of course, is likely a goner, or, at best, will be incomplete.
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Old 09-08-2009, 12:13 AM
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Just a brief followup about this:

Quote:
Originally Posted by Sophie View Post
At the prices for a UPS rated long enough to let unaccompanied backup jobs complete,
It's wouldn't be necessary to have a UPS with that much battery reserve, just enough to keep a system running long enough to do a clean manual or automatic shutdown before completely losing power.

I'd much rather have controlled shutdowns than abrupt, uncontrolled ones interrupting backups (and other system activity) in progress.

Also:

Quote:
… I really do not want to put multiple big, expensive, and ugly UPS boxes throughout my home …
That almost sounds like you're living in a mansion.

I'm curious how many non-portable Macs you have and their models. Are they sleeping or fully shutdown when not in use? Even if having UPS for all of them is impractical maybe it's a justifiable benefit for some of them?

If I had an iMac in the kitchen, for example, I'd limit the amount/type of data on it requiring a backup regardless if it used a UPS (and likely only used if it could be installed non-intrusively). Or, I'd consider using a portable Mac there instead and have the benefit of its battery kicking in during power outages.

This discussion can end if you're set against using any UPS. If you're open to the possibility then people may be able to help you find an acceptable usage strategy within your environment and specific limitations. However, that would stretch the topic beyond being SuperDuper!-related and could make it inappropriate for public discussion here.
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