Q: Just how quick is Apple’s Time Machine?
A: Way faster than you can do with OS/X command line tools.
The headline is that command line tools take 80 minutes to do what Time Machine does in 3-10 mins.
TimeMachine does this in 3mins (1st log example) or 10 mins (2nd log example),
vs 38mins for “cp -al” + 42mins for rsync. [80 mins]
While there’s only 40Mb-50Mb in actual directory entries [2.1M * 21ch], which can notionally be written in seconds, each directory takes one block minimum on disk, plus an inode. I wasn’t able to quickly discover the size of an in ode. In V6 Unix, it was 512by, from memory.
Finder’s “Get Info” on any small file shows the “Allocation Unit” - 4Kb on my HFS+ volumes.
or "/usr/bin/stat -f %k .” - the ‘optimum’ block size for a volume.
That’s 1.4GB, minimum, to be written. [360,000 * 4Kb = 360 * 4MB = 1.4GB]
Wikipedia maintains that HFS+ allows hard-links of directories to support Time Machine. This was removed from Unix pre SVR4 to prevent “cycles” in filesystems (infinite recursion).
Outputs from my Mac Mini, OS/X Mavericks.
Details:
Internal 300GB 2.5" drive, external USB 1TB 2.5" drive. Both 5400RPM
358,00 directories and 2.1M files
$ uname -a
Darwin mini 13.2.0 Darwin Kernel Version 13.2.0: Thu Apr 17 23:03:13 PDT 2014; root:xnu-2422.100.13~1/RELEASE_X86_64 x86_64
$ sudo cp -a / /Volume/SJ-1TB-2014/bkup/last# full initial copy to USB drive
real 574m59.327s
user 0m57.402s
sys 26m43.417s
mini:SJ-1TB-2014 steve$ df -h .
Filesystem Size Used Avail Capacity iused ifree %iused Mounted on
/dev/disk2s1 932Gi 262Gi 669Gi 29% 68776493 175413457 28% /Volumes/SJ-1TB-2014
mini:SJ-1TB-2014 steve$ df -h /
Filesystem Size Used Avail Capacity iused ifree %iused Mounted on
/dev/disk0s2 297Gi 250Gi 47Gi 85% 65515369 12417533 84% /
mini:SJ-1TB-2014 steve$ time sudo gcp -al bkup/last/ bkup/new # Apple's "cp" does not support "-l" option. This used gnu's "cp" from Darwin Ports.
real 38m53.462s
user 0m19.785s
sys 7m2.447s
Try 2: [user & sys time similar, no explanation of longer elapsed time]
real 68m13.564s, user 0m22.919s, sys 7m35.730s
mini:SJ-1TB-2014 steve$ df -h .
Filesystem Size Used Avail Capacity iused ifree %iused Mounted on
/dev/disk2s1 932Gi 264Gi 667Gi 29% 69220039 174969911 28% /Volumes/SJ-1TB-2014
Fri 4 Jul 2014 14:09:28 EST
mini:SJ-1TB-2014 steve$ time sudo rsync -aHSx / bkup/new # trimmed errors
rsync warning: some files vanished before they could be transferred (code 24) at /SourceCache/rsync/rsync-42/rsync/main.c(992) [sender=2.6.9]
real 41m0.578s
user 1m24.502s
sys 8m25.340s
$ time sudo rm -rf bkup/new
real 52m32.459s
user 0m10.641s
sys 5m31.523s
Dirs - 360,000
# time find bkup/last -type d|wc -l # added commas
358,314
real 12m39.225s
user 0m7.775s
sys 2m55.545s
Files - 2.1M
# time find bkup/last -type f|wc -l # added commas
2,109,216
real 13m31.380s
user 0m8.334s
sys 2m54.752s
Time Machine logs, using command:
$ grep com.apple.backupd /var/log/system.log [selected and trimmed]
2.5 minutes, no system activity, trimmed
Jul 4 09:06:37 mini com.apple.backupd[33481]: Starting automatic backup
Jul 4 09:08:06 mini com.apple.backupd[33481]: Copied 245 items (9.3 MB) from volume Macintosh HD. Linked 3392.
Jul 4 09:08:36 mini com.apple.backupd[33481]: Copied 35 items (2 KB) from volume Macintosh HD. Linked 582.
Jul 4 09:08:52 mini com.apple.backupd[33481]: Backup completed successfully.
10.5 minutes, system active. full log.
Jul 4 10:10:05 mini com.apple.backupd[34131]: Starting automatic backup
Jul 4 10:10:08 mini com.apple.backupd[34131]: Backing up to /dev/disk1s1: /Volumes/SJ-1TB-SG/Backups.backupdb
Jul 4 10:10:20 mini com.apple.backupd[34131]: Will copy (13.6 MB) from Macintosh HD
Jul 4 10:10:20 mini com.apple.backupd[34131]: Found 202 files (13.6 MB) needing backup
Jul 4 10:10:20 mini com.apple.backupd[34131]: 2.97 GB required (including padding), 321.67 GB available
Jul 4 10:16:38 mini com.apple.backupd[34131]: Copied 377 items (13.6 MB) from volume Macintosh HD. Linked 3548.
Jul 4 10:16:49 mini com.apple.backupd[34131]: Will copy (19.3 MB) from Macintosh HD
Jul 4 10:16:49 mini com.apple.backupd[34131]: Found 131 files (19.3 MB) needing backup
Jul 4 10:16:49 mini com.apple.backupd[34131]: 2.97 GB required (including padding), 321.66 GB available
Jul 4 10:19:16 mini com.apple.backupd[34131]: Copied 310 items (19.3 MB) from volume Macintosh HD. Linked 2862.
Jul 4 10:19:50 mini com.apple.backupd[34131]: Created new backup: 2014-07-04-101949
Jul 4 10:20:33 mini com.apple.backupd[34131]: Starting post-backup thinning
Jul 4 10:20:33 mini com.apple.backupd[34131]: No post-backup thinning needed: no expired backups exist
Jul 4 10:20:33 mini com.apple.backupd[34131]: Backup completed successfully.
7.5 minutes, system active, trimmed
Jul 4 14:39:33 mini com.apple.backupd[37148]: Starting automatic backup
Jul 4 14:44:45 mini com.apple.backupd[37148]: Created new backup: 2014-07-04-144444
Jul 4 14:45:29 mini com.apple.backupd[37148]: Starting post-backup thinning
Jul 4 14:47:02 mini com.apple.backupd[37148]: Deleted /Volumes/SJ-1TB-SG/Backups.backupdb/mini too/2014-07-03-134254 (8.2 MB)
Jul 4 14:47:02 mini com.apple.backupd[37148]: Post-backup thinning complete: 1 expired backups removed
Jul 4 14:47:05 mini com.apple.backupd[37148]: Backup completed successfully.
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