Comments on: Time Machine vs. ZFS + rsync

By: Microdermabrasion

Microdermabrasion — Tue, 17 Mar 2009 17:27:23 +0000

You got excellent writing skills. Awesome article. I enjoyed every word of it. Thanks:)

By: Microdermabrasion Machine

Microdermabrasion Machine — Thu, 26 Feb 2009 05:41:05 +0000

Hmmm.. Interesting:)

By: Ralph P Dickerson

Ralph P Dickerson — Wed, 11 Feb 2009 04:10:27 +0000

your blog is great!

By: Nakia J Bryden

Nakia J Bryden — Tue, 10 Feb 2009 04:06:04 +0000

great article!, grats for u site

By: sam

sam — Mon, 15 Dec 2008 22:16:07 +0000

I haven’t done any more work on it but I am running it 24/7 on 2 of my machines (a MacPro and a Macbook Air) and the overhead seems to be very low. As for incremental deletes I basically decided that I would just run the full backup periodically rather than add the functionality. Full volume backups I believe are possible as I just recently used rsync to move my bootdisk. You need some additional parameters to make it work: rsync -xrlptgoEv did all that it needed to make a full backup.

Sam

Reference: http://rna.urmc.rochester.edu/john/public/pages/backup%20Mac%20easy%20methods.html

By: Jeff

Jeff — Sun, 14 Dec 2008 01:54:02 +0000

Great article! I’ve been looking for a way to use fsevent with rsync for months now, and as far as I know, you are the first to hack something together. It’s been a little while since your post, so I’m wondering if you have any updates or have made any improvements to the script? For example, implementing incremental deletes or allowing full volume “/” backups? Also, I’m curious what sort of additional overhead running fslogger constantly between backups creates?

I started experimenting with rsync to ZFS a while back, but ended up coming back to Time Machine for varying reasons, (one being so I could use the AirDisk I have connected to my Airport Extreme and not run a whole ZFS server, another some compatibility issues between Mac meta-data and OpenSolaris or FreeBSD). However, I’m once again becoming frustrated at the time and resources it takes to do an hourly TM backup – wouldn’t it be nice to just send file deltas! I would be interested whether it would be possible to alter the script to edit out ZFS, and to backup an entire volume to a HFS+ disk image on an AirDisk, either performing hard-linked snapshots (a la rsnapshot) or just a regular, non-versioned backup. Unfortunately, I’m not a programmer, so I would have no idea where to begin. Great script though, and I look forward to testing it out with ZFS.

By: sam

sam — Sat, 01 Nov 2008 00:06:32 +0000

@Cristian: 1) Didn’t mean to imply that they were new, but they are new to the Mac. 2) That is ideal for a ZFS only environment — hoping we can do just that in Snow Leopard. Right now though I’m still on Leopard and using HFS+ as my main filesystem.

By: Cristian Yxen

Cristian Yxen — Fri, 31 Oct 2008 23:44:11 +0000

1. Snapshots are not something new, other filesystems have this feature for years. UFS2 for example.

2. No need for rsync and scanning your full harddrive if your local disk is ZFS too. ZFS includes the feature of incremental snapshots which can be copied and appended to ZFS filesystem on another disk or remote filesystem.

So the way would be:

1) make a ZFS snapshot on your local disk
2) send the initial snapshot to the backup disk
3) take more snapshots on your local disk
4) copy the incremental snapshot (only including differences between two snapshot) to the backup disk

By: sam

sam — Fri, 31 Oct 2008 17:15:00 +0000

@Mark: I am backing up to ZFS running on my Mac OS X box using the latest bits from http://zfs.macosforge.org/trac/wiki/ along with the Mac version of rsync on both sides. Additionally, I am only backing up things in my Users directory — no system files, do I still need the additional flags?

@ssp: I actually think it would be quite system to use this tool http://www.osxbook.com/software/fslogger/ to track filesystem changes which would allow the rsync solution to be just that much better. Looks like I’ll need to put a nice UI on it as well.

By: ssp

ssp — Fri, 31 Oct 2008 16:52:08 +0000

Actually Time Machine is even worse than what you state as it seems to determine whether a file has changed solely by looking at its modification date and size. In particular Time Machine will not discover changes in a file in case its modification date didn’t change. Also, conceptually (as opposed to file system snapshots, I suppose), Time Machine’s behaviour when you change ownership of or access permissions to folders is probably less than desirable as well.

All the more reasons for a better way to do backups like the one you present. But Time Machine’s advantage of making the creation of a backup really trivial and without scanning your full drive is hard to compete with.