Q: What is the fastest way to update (duplicate) offsite Time Machine backups?
I have an external hard drive constantly plugged into my iMac which serves as a target for the hourly Time Machine backups, and to prevent catastrophic data loss in case of something like a tornado or house fire, I keep a second external hard drive offsite and bring it home once a week in order to copy my Time Machine backups over to it.
Currently I use the steps for copying a Time Machine database to a new drive as described by Apple; however, their instructions are geared toward migrating to a new/larger backup drive as a one time (or at least, not very frequent) event, and aren't ideal for routine updating of a second drive that already contains an older version of the backup file.
After initiating the copy procedure by dragging and dropping the backup from one drive to the other, Finder takes 2-4 hours to index the millions of sparse bundles it contains, then I have to be around to "authenticate" the copy command, wait a few more minutes until I can accept the prompt to replace the existing file, and finally Finder actually begins copying the backup file, which takes 8-16 hours to complete (for less than 400GB over USB 3).
Besides the wear on my computer and drives from having to run from 10-20 hours straight every week for this backup alone, it seems a bit ridiculous having to copy the entire backup every week when probably greater than 97% of the files already exist on the target drive. I've been looking around online for a while and found some articles about manipulating a previous version of Carbon Copy Cloner to handle Time Machine backup files, but I have the current version which no longer does this.
Is there a better/faster way to update offsite drives with Time Machine backups (that already contain most of the backup file), or am I destined to the irritating process described above if I want to keep an incremental backup offsite?
(I use CCC to also keep a bootable backup offsite, but CCC's backups aren't incremental.)
iMac with Retina 5K display, OS X Yosemite (10.10.5)
Posted on Jan 6, 2016 12:14 AM