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View Full Version : SD/TM: "soft" stopping


etanter
06-09-2009, 07:13 PM
Hi,

I'm moving away from Time Capsule for my whole system backup (although it works fine, it's really too slow). I appreciate the speed of Smart Update.

[Actually, it's fast enough that one could want to schedule a smart update every couple of hours (like TM does), but strangely enough the scheduler of SD assumes one only wants to schedule once a day (why is that? easy fix?)]

One thing that is valuable about TM is that it "knows" how to stop whenever the user decides to stop the machine. ie. if I need to leave out of a rush with may laptop and the backup is running, I can just stop it. It will manage to restart afterwards, consistently.

This does not seem possible with SD. If I stop, I get a scary warning that the drive will be left in an unknown state.

Is there something to do? Couldn't SD have a special "soft" mode where one can stop it when needed (I understand that this may imply some additional space/time requirements for the whole, but I may be willing to pay for those)

Thanks,

-- Éric

sjk
06-09-2009, 09:48 PM
If I stop, I get a scary warning that the drive will be left in an unknown state.
I interpret it to mean that interrupting a backup can leave the copy in a state where restoring from it can have negatively unpredictable results. But the next Smart Update to that copy that successfully finishes will leave it in a known, usable state.

Restoring from an interrupted, incomplete Smart Update backup can leave the destination with an unexpected mix of files that had been properly backed up plus earlier versions that should have been backed up before the interruption.

If that doesn't make sense Dave or someone else probably has an easier-to-understand explanation.

chris_johnsen
06-10-2009, 02:46 AM
That is also my understanding. A stopped SD! backup will leave the destination with some "new" files (ones copied before it is stopped) and some "old" files (those not yet processed before the backup is stopped). Depending on what is old and what is new, the system may work fine and just some of your data files will not be the most recent. But if it is interrupted in the middle of copying (for example) /System or /Library (or it has already copied one but not the other), then the OS may be in an inconsistent state.

An interrupted backup should be OK to use to grab individual data files, it is just not 100% safe to use it as a full restore. The filesystem itself will be OK, it is just the destination will not been a fully consistent "snapshot in time" of the source.

The next complete SD! backup will fix any inconsistency that may have been left behind.

sjk
06-10-2009, 04:13 AM
Thanks for that followup explanation, Chris. Much clearer than mine, including to me. :)

dnanian
06-10-2009, 05:55 AM
Both Chris and sjk are right: it's "unknown" in the sense that the content is a not a complete backup and can't be relied upon as such. But it's not going to do any physical damage to the drive or filesystem.

etanter
06-10-2009, 11:20 AM
Thanks to all, that clarifies things up (and it makes sense).

-- Éric

sjk
06-10-2009, 03:17 PM
Maybe the dialog warning could be rewritten to seem less scary? Don't ask me to volunteer; Chris and Dave are better candidates. :)

etanter
06-10-2009, 03:21 PM
That would be a very good idea indeed. Following the "full/clear explanations" of the rest of the UI, it makes sense.

-- Éric

dnanian
06-11-2009, 06:40 AM
It's something I've been considering: never liked this particular warning. It's logged, in any case...