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jefman 05-25-2007 09:25 PM

SD "copy all files" vs. Disk Utility "restore"
hi -

i'd like to know what the differences are between using SD! "erase and copy" with "copy all files", and using Disk Utility's "restore" command to create a full backup on a firewire partition.

until now i've been using SD! to back up only important files to a sparse image.

i recently bought a second firewire drive, and decided to follow the advice in the manual to make a backup partition on it. then i decided to just try out booting from the tiger install disk, and using Disk Utility "restore" to copy my internal drive to the backup partition. i heard that this is the fastest way to make a complete bootable backup, since it does a "block copy".

i haven't yet tried using SD! to do the same thing. but now i'm wondering if just using Disk Utility like this might be the path of least resistance... how much slower would SD! be, assuming i don't use smart update? are there advantages to using SD!'s method, over the Disk Utility block copy?

related to this, are there any rules of thumb about how big to make the backup partition? is it necessary for it to be exactly the same size as the internal drive? i read that SD! doesn't need it to be, but what if i had to use Disk Utility to back up or restore?


dnanian 05-25-2007 09:32 PM

Since this really isn't an SD question, I'm not sure this is the best place to be asking. But, one big advantage is that you can schedule SD, and use it when you're running from the drive.

Backups don't usually do you much good if you don't do them. And if you need to start up from another drive to back up, you're not likely to do so...

jefman 05-26-2007 05:24 PM

hi - sorry if my question wasn't appropriate for this forum. i've never used the cloning method of backups before. i'm trying to understand the difference between a clone made with SD, and one made with Disk Utility. just the fact that there *is* a difference makes me want to know what's really going on with my backups. is there somewhere else i should ask about this?

basically i'm trying to understand all the variables, so i can make an informed decision about the best backup strategy for me.

for example, i read that SD doesn't copy certain system files that apple recommends not to. presumably Disk Utility does, if it's doing a block copy. does that make any difference to anything? could one use Disk Utility to make the initial clone (for speed), then use SD with "smart update" to update it, or would there be some incompatibility? i also wondered if SD's cloning method is somehow more (or less) safe or accurate than a block copy. and there seemed to be an issue with Disk Utility making folders like /etc visible when they shouldn't be, whereas SD doesn't have this problem. and... what else might i be missing?

my other question was about the size of the backup partition. it seemed like it might be a good idea to make it larger than the source drive, to give it extra "working space", as discussed in the troubleshooting section. i do tend to keep my internal drive chock full. but then i noticed a lot of people in the forum are using Disk Utility to restore their backups to the internal drive when there's trouble. i don't really know what the reason for that is, but i guess there must be one? - and i wondered if having mismatched partition sizes would prevent this from working in case i needed it to.

i'm sure most of these things are irrelevant. but the thing is, the only way to test it all is to make a backup and then restore it. and if i've done something wrong along the way, i risk losing everything. so i guess i'm being a bit paranoid about making sure i do everything right the first time.

dnanian 05-26-2007 05:33 PM

A block copy copies things well below the file level, at the physical block level of the drive. This means that the drive is copied pretty much exactly as-is, including corrupted folders, fragmentation, temporary files, VM swap files, etc.

Every time you copy this way, you copy the whole drive. It takes quite a lot of time: well more than your typical smart update. On top of that, you have to boot from some other drive. But the advantage is that things that operate below the file system or are dependant on low-level file system details (e.g. copy protected applications that lock to your drive) don't (usually) need to be reactivated.

People use Disk Utility to restore when they've backed up to something that's not bootable. A SuperDuper! copy is a volume just like any other, and can be restored by Disk Utility: that's one of SD!'s advantages.

As far as partition sizes go, SD! doesn't care unless things are way too full, as you read. I think that Disk Utility does different types of low-level copies depending on whether or not the volumes are the same size, but I'm not sure.

jefman 06-02-2007 08:30 AM

ok, thanks for all the info! more food for thought...

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