This morning my Mac’s backup (time machine) reported that the backup disk (a sparse bundle on a time machine) was read only and it couldn’t backup. A bit later I noticed the error was more serious: “The disk “Backup of Pra…” was not repairable by this computer. It is being made available to you with limited funtionality. You must backup your data and reformat the disk as soon as possible.” (sic).
So I fired up Disk Utility; hit open; browsed to find that sparse disk image. Found it. But, it wasn’t available to open; grayed out. Browsing the web I found the suggestion that I should drag the image into Disk Utility’s window – that opened it.
At that point I tried letting disk utility try to repair the sparse image. No luck “Invalid sibling link.” Argh. I found a posting that implies I can buy a more potent disk repair utility ($50), but instead I’m just going to discard the backups and start over.
This, and reading various postings about the problems people are having with their Time Machine backups is quite distressing.
I gave up on time machine a few months ago. It used up 50% of computing resources constantly, doing who-knows-what. At home, the network drive it was backing up to was always going offline, and it was constantly a problem. I had no confidence that it was actually backing up, and the backup itself is an opaque blob. I went back to nightly rsyncs over the network, and now I am much happier.
It would be better if Apple had a copy on write file system with snapshots, like we had on the NetApp back in the second millenium.
I’m using rdiff-backup + rdiffweb once a week at work to supplement our amanda tape backups. After the initial backup incremental use is quite small, as it compresses old versions. After 5 months of weekly backing up 715GB of data the incrementals only use 113GB, for a total of 828GB. There’s only 90GB left on the drive though, since a 1TB drive is 917GiB 🙁