Syncing two Macs via a Network Drive with a Different Filesystem

Discussion in 'macOS' started by ArthurDaley, May 13, 2010.

  1. ArthurDaley macrumors regular

    Feb 29, 2008
    I've been looking at how to sync my two Macs.

    There are lots of options out there but none I'm comfortable with:

    1. DropBox. It appears that what people do is put their data files into the DropBox folder locally (or make symbolic links to that folder) and DropBox then monitors this folder locally, if changes are made it propogates the changes to their server and then out to other machines/devices under your account. I could be wrong and it monitors both local and server. Anyhow the trouble I have is that I've got tens of gigs and I don't see why I should ever have to take the bandwidth/time/security hit of using the Internet as the go-between. Plus I'm uncomfortable with DropBox acting as a blackbox; i.e. no idea the logic it's using to determine changes, determine conflicts or manage resolution.
    2. JungleDisk/BackBlaze with Chronosync. Using Chronosync means that you have full control and transparency, i.e. know logic and have logs. I was going to put aside my concerns of using cloud storage (bandwidth/accessibility/security), however JungleDisk just purged around 60 gig of my data because a 2USD invoice failed to process and I was completely unaware of the invoice processing failure. So for now, cloud storage is out. (if I do go to cloud, I'll try BackBlaze next time as JungleDisk clearly can't be trusted)
    3. Sync over LAN between two Macs (e.g. via Bonjour) and use Chronosync to perform the sync. Not a bad setup, but I've got the feeling that placing a third disk in between, is somehow cleaner and gives overall better protection.

    Therefore I've decided to keep two Macs in sync, to use Chronosync plus a NAS (in my case a QNAP 639-pro) as the middle man.

    Others must have done a similar setup (after all it's just a variation on using an external drive as the middle ground).

    So some preliminary questions are:

    1. do I need to be concerned that the NAS uses EXT3 (Linux) fielsystem; i.e. will ownership/group permissions or extended file attributes be an issue?
    2. Is there an issue with not syncing file metadata (.ds_store files comes to mind)?
    3. Syncs take a very long time when you've got tens of gigs, however often it's just a handful of files changing, i.e. OmniFocus, Devonthink, 1Password plus a few active project files. So it seems it's a good idea to have a full sync and some quick sync. Do people have a similar setup and can describe their Chronosync configs?
    4. It would appear the safest option is to close down 1password, OmniFocus etc. on one machine before hitting sync on that machine, but this introduces overhead, but I guess it depends on how the likes of 1Password writes to file and when

    Thoughts appreciated.
  2. Hal Itosis macrumors 6502a

    Hal Itosis

    Feb 20, 2010
    Perhaps you know this already (but i don't see any mention): the whole business about owner/group/permission/metadata/attributes is usually dealt with by using a disk image (e.g., that's how Time Machine + Time Capsule handle backups).
  3. ArthurDaley thread starter macrumors regular

    Feb 29, 2008
    No I did not.

    I might add that the 60 gig of files I want to sync via the NAS are all contained in 3 *20 gig encrypted bundle sparse images.

    So maybe it's best not to sync the opened images but the sparse bundles, so I'll presume that the sparse bundles are out of date on the local machine until I "eject" the corresponding volume? i.e. I have to "eject" the expanded volume to update the sparse bundles before I hit sync?

    Edit, just ran into this

    I have had a big enough consistency catastrophe with one of my big sparsebundles, though, that I've sworn off them for now. The problem I had basically stems from the fact that even when the sparsebundle is mounted, its band files are not all always marked as busy. So, they'll sync in real time, and if something happens (like the computer crashes, or a gremlin touches one of the band files on another computer), you can quickly wind up with an inconsistent image that is very difficult to repair. The nice thing about sparseimages is that the whole disk image is marked busy until it is unmounted, so Dropbox won't try to index or sync it at all until it's been unmounted and in a consistent state.

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