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Author Topic: Time Machine clarification  (Read 2168 times)

dimitri_b

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Time Machine clarification
« on: June 13, 2012, 07:41:55 AM »
Espionage 3 announcement mentioned that this new version works better with Time Machine. I tried to make some sense out of this and out of what I observed by examining Time Machine backups, and I have a few questions?

1)when the encrypted folder/image is unlocked/mounted, will Time Machine back up its unencrypted contents?
2)does the above folder/image need to be, or can it be, excluded from TM backup via TM options?
3)does the image itself (the .sparcebundle file in Espionage library folder) need to be locked for TM to back it up, as was the case with Espionage 2 built-in backup?
3)TM is supposed to do incremental backup, does it also work with Espionage .sparcebundle files, i.e. images located in Espionage 3 library folder? In other words, if I have 1000 files in the folder taking up 1Gb, but only one of the files changes - will TM back up the whole 1Gb, or just a segment?
« Last Edit: December 31, 1969, 11:00:00 PM by Guest »

zsolt

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Re: Time Machine clarification
« Reply #1 on: June 14, 2012, 11:23:34 AM »
Hello dimitri_b

Here we go:
Quote
1)when the encrypted folder/image is unlocked/mounted, will Time Machine back up its unencrypted contents?
no

Quote
2)does the above folder/image need to be, or can it be, excluded from TM backup via TM options?
no need, all works fine, the unlocked folder's content will not be saved, and the disk image will be backed up unless you exclude Library/Application Support/Espionage/Data folder from your backups, or some other path which you used to store Espionage disk images

Quote
3)does the image itself (the .sparcebundle file in Espionage library folder) need to be locked for TM to back it up, as was the case with Espionage 2 built-in backup?
no

Quote
3)TM is supposed to do incremental backup, does it also work with Espionage .sparcebundle files, i.e. images located in Espionage 3 library folder? In other words, if I have 1000 files in the folder taking up 1Gb, but only one of the files changes - will TM back up the whole 1Gb, or just a segment?
sparse bundle disk images are not plain files, they are folders (make a right click on them and select show contents), and you will see a folder named bands. So the data in the disk image is broken down in separate "band" files, which are added if you add more data to disk image, or are changed, but only those which contain data you change. So TimeMachine will detect the changed bands and backup only those, this would be an incremental backup.

I have/had only one doubt, and this is: what happens if you are writing into the disk image at the time it is saved, so I tested it now and here is what happened:
I unlocked the folder and started a download into it and then started a backup too.
The download was surely running during the time backup took place, but was finished a short time before the backup finished.
I kept the time machine menu open to monitor what is going on with backup and noted something interesting...I saw this few times before already but did not pay attention to this...
TM says it has say 100MB to backup, starts the backup and counts, but then when it reaches 100MB it says, say 20MB and moves on, does not finish the backup and start again, just moves on in the same session.
So what I suppose happens is that TM does a list of files to be saved before the backups starts (during the stage "preparing backup" but during backup it detects that the file size changed, so it skips it temporarily, once the backup is done, it goes back and check if the files which were changing are of a fix size now, and if yes then saves them in the same session.
So at the end in the latest backup I had the disk image which contained the full amount of downloaded data....
Sure we could test this further, for example, what happens if the download does not finish before the backup finishes, I assume then TM would simply not save the bands which are being written to, so you would get a disk image which does not contain the active download. If it would be a copy of many small files then the backup would again contain only the files which were completely copied at the time the backup finished....
The most important thing to be sure will not happen, is that the fact that the data is being written, does not produce a corrupted disk image, and it seems it will not.

Let me know if you have further questions.

Zsolt
« Last Edit: December 31, 1969, 11:00:00 PM by Guest »
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dimitri_b

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Re: Time Machine clarification
« Reply #2 on: June 14, 2012, 09:22:46 PM »
Thank you, Zsolt,

That was very informative, I have no further questions or concerns with TM.
« Last Edit: December 31, 1969, 11:00:00 PM by Guest »

zsolt

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Re: Time Machine clarification
« Reply #3 on: June 15, 2012, 06:32:20 AM »
Great, I'm glad you are satisfied, thanks for confirmation that all is fine now.
« Last Edit: December 31, 1969, 11:00:00 PM by Guest »
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