Disk Maintenance before backup?

[t3rockhall]

Does it make sense to, say, run TechTools4 plus defrag before making a Smart Backup? Or only a full erase and copy backup? Or it isn't needed at all?

If I defrag, backup to the external and then update the Mac at my vacation home with the backup, is all that time wasted?

Just curious.

[dnanian]

Not really, no. In general, I don't see any reason to defrag until you know defragmentation is significant.

[t3rockhall]

But, the question is, does running TT4 on the Mac's internal HD have any effect on the data that's being placed on the external b/u HD?

Will originally fragmented files be backed up in the same fragments, or will they be "put back together" by SD?

[dnanian]

It has no effect whatsoever. The two devices fragment below the file level, and we copy at the file level. So, after a while, the backup will become fragmented.

If you do an erase-then-copy, the files will be copied contiguously, regardless of how they lie on the source, because the file system isn't fragmented.

[t3rockhall]

Soooooo, Every now and then I should do an erase and copy to the external, and that will defrag the files on the external drive. OR, just ignore the external drive and just do an erase and copy back to the internal, and THAT will defrag the files on the internal.

But this takes about an hour. I can "defrag files only" in TT4, which takes a lot less time.

But only the files, and not the "empty" disk spaces.

So from a time standpoint, I'm better off running TT4 once in a while and that's that.

Do I understand this correctly?

[dnanian]

Yes. But I don't think you need to defrag, for the most part. The system defragments files automatically. Not all files, but most.

When things are slowing down, sure, go ahead and do it. But no need to do it "routinely"...