Yesterday, an interesting discussion about file metadata has begun on darwin-dev. Apple’s Jordan Hubbard argued how file creation dates should not be preserved when copying files.
In this piece, I counter that treating file creation dates as first-class metadata citizens and preserving them upon copying is the more sensible thing to do, and eventually represents the behavior expected by most Mac users.
Categories: macosx, unix, hacking
Continue Reading June 27th, 2006
Earlier, I wrote about The State of Backup and Cloning Tools under Mac OS X, where I made the point that copying files on Mac OS X is not trivial because of the metadata associated with files.
I analyzed a variety of file copying engines, most of them command-line tools, and demonstrated how they fare in preserving file metadata.
In this article, I will investigate commonly used GUI backup/cloning tools for Mac OS X. The tools vary widely with respect to their feature set; the features are irrelevant here. I will concentrate purely on the underlying functionality of copying files. A backup tool needs to be able to copy files faithfully for a successful restore in case desaster has struck. The surprising conclusion of my investigation is that almost all Macintosh Backup tools fail at their most basic task, the faithful copying of files.
Categories: macosx, hacking
Continue Reading April 23rd, 2006
Introduction
Back in the days of OS 9, backing up files was fairly easy. One would just use the Finder to copy files and directories to another volume, and be done. The simplicity, unfortunately, is gone with OS X. Such a simplistic approach is no longer a guarantee to preserve all data faithfully (neither is it a simple or reliable approach for a regular backup procedure). The trouble on OS X is mostly related to metadata, i.e., data about files and directories (such as modification date, file creator/type, Unix permissions, etc.).
Another problem arises when a complete system partition shall be backed up and be bootable later on. Making a backup bootable is not trivial.
Superficially, one could nourish high expectations about the state of backup solutions on Mac OS X, because the underlying BSD Unix core has made all the mature backup and file copying tools that have been developed for Unix systems available on the platform. However, the fly in the ointment is that these tools are generally not aware of Mac OS X metadata and, hence, fail to produce a faithful backup.
This essay will first investigate means to copy files as completely and reliably as possible on Mac OS X, if possible with free and open-source tools. It will conclude with an (incomplete) survey of dedicated backup tools. The tools covered are not only relevant for backup purposes, but also for the case of migrating machines, when the content of one hard drive is to be cloned to another one.
I will not address common features of backup software such as scheduling, backup management, and incremental backups. This piece will be solely about the bare basics of copying files.
The analysis presented here assumes a recent install of OS X 10.4.5 (Tiger) with all updates. The state of backup and cloning tools has already been worse, so there is no need to shoot ourselves into the foot by using outdated tools.
(more…)
Tags: apple, asr, backup, cloning, ditto, mac os x, metadata, rsync, superduper, tiger
Categories: macosx, unix, hacking
March 5th, 2006
