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Notes of reassurance concerning Mobile Time Machine local snapshots.
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Graham Perrin
Graham Perrin
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Real time visualisation of file system activity

fseventer

http://fernlightning.com/doku.php?id=software:fseventer:start

If you use Lion

Mobile Time Machine

Local disk space will be used, intelligently — never so much to cause an alert from the system. If you're curious, you can run two commands in Terminal:

man mtmd

q

tail -f /private/var/log/system.log | grep -E 'backup|mtm'

— set that Terminal window aside, leave it in background, work normally for an hour or so. What's logged should reassure you. When satisfied/finished, bring the Terminal window to foreground then to interrupt the running command:

controlc

Misconceptions of the Mobile Time Machine file system

In Mac OS X 10.7 Lion: the Ars Technica review (page 18) (2011-07-20) there's perception of an overlap, a description of something as suboptimal, and talk of copies.

The notion of local disk space being used for copies may be understandably alarming — "copying something takes time, places load on the CPU" and other such thoughts.

I suspect that Lion's use of NFS for Mobile Time Machine local snapshots will prove to be not comparable to copying, in that sense. Suspect a very intelligent use of space that involves neither copying nor movement of files — the magic done at catalog B-tree and related levels on the HFS+ volume, and at some level in mtmfs.

[macbookpro08:~] gjp22% date
Tue  2 Aug 2011 15:13:04 BST
[macbookpro08:~] gjp22% uname -a
Darwin macbookpro08.centrim.freeman-centre.ac.uk 11.0.0 Darwin Kernel Version 11.0.0: Sat Jun 18 12:56:35 PDT 2011; root:xnu-1699.22.73~1/RELEASE_X86_64 x86_64
[macbookpro08:~] gjp22% sudo fileXray --volume_header /Volumes/MobileBackups
Could not determine an appropriate HFS+ volume from "/Volumes/MobileBackups". The file system type of /Volumes/MobileBackups is 'mtmfs'.

To sum up: after initial concerns are set aside, most people should find local snapshots to be a good thing, with an impact on performance that is either imperceptible or negligible.

FileVault 1 in Snow Leopard or Lion

In more modern versions of the operating system, use of bands for FileVault 1 should be not problematic. AFAIR space is freed dynamically, without the need to log out.

Whether free space was as well managed with FileVault 1 two years ago, when the question was posted, I can't recall.

Real time visualisation of file system activity

fseventer

http://fernlightning.com/doku.php?id=software:fseventer:start

If you use Lion

Mobile Time Machine

Local disk space will be used, intelligently — never so much to cause an alert from the system. If you're curious, you can run two commands in Terminal:

man mtmd

q

tail -f /private/var/log/system.log | grep -E 'backup|mtm'

— set that Terminal window aside, leave it in background, work normally for an hour or so. What's logged should reassure you. When satisfied/finished, bring the Terminal window to foreground then to interrupt the running command:

controlc

FileVault 1 in Snow Leopard or Lion

In more modern versions of the operating system, use of bands for FileVault 1 should be not problematic. AFAIR space is freed dynamically, without the need to log out.

Whether free space was as well managed with FileVault 1 two years ago, when the question was posted, I can't recall.

Real time visualisation of file system activity

fseventer

http://fernlightning.com/doku.php?id=software:fseventer:start

If you use Lion

Mobile Time Machine

Local disk space will be used, intelligently — never so much to cause an alert from the system. If you're curious, you can run two commands in Terminal:

man mtmd

q

tail -f /private/var/log/system.log | grep -E 'backup|mtm'

— set that Terminal window aside, leave it in background, work normally for an hour or so. What's logged should reassure you. When satisfied/finished, bring the Terminal window to foreground then interrupt the running command:

controlc

Misconceptions of the Mobile Time Machine file system

In Mac OS X 10.7 Lion: the Ars Technica review (page 18) (2011-07-20) there's perception of an overlap, a description of something as suboptimal, and talk of copies.

The notion of local disk space being used for copies may be understandably alarming — "copying something takes time, places load on the CPU" and other such thoughts.

I suspect that Lion's use of NFS for Mobile Time Machine local snapshots will prove to be not comparable to copying, in that sense. Suspect a very intelligent use of space that involves neither copying nor movement of files — the magic done at catalog B-tree and related levels on the HFS+ volume, and at some level in mtmfs.

[macbookpro08:~] gjp22% date
Tue  2 Aug 2011 15:13:04 BST
[macbookpro08:~] gjp22% uname -a
Darwin macbookpro08.centrim.freeman-centre.ac.uk 11.0.0 Darwin Kernel Version 11.0.0: Sat Jun 18 12:56:35 PDT 2011; root:xnu-1699.22.73~1/RELEASE_X86_64 x86_64
[macbookpro08:~] gjp22% sudo fileXray --volume_header /Volumes/MobileBackups
Could not determine an appropriate HFS+ volume from "/Volumes/MobileBackups". The file system type of /Volumes/MobileBackups is 'mtmfs'.

To sum up: after initial concerns are set aside, most people should find local snapshots to be a good thing, with an impact on performance that is either imperceptible or negligible.

FileVault 1 in Snow Leopard or Lion

In more modern versions of the operating system, use of bands for FileVault 1 should be not problematic. AFAIR space is freed dynamically, without the need to log out.

Whether free space was as well managed with FileVault 1 two years ago, when the question was posted, I can't recall.

Removed a question from my answer. That question now appears as a comment under the opening question.
Source Link
Graham Perrin
Graham Perrin
  • 7.8k
  • 14
  • 83
  • 246

Real time visualisation of file system activity

fseventer

http://fernlightning.com/doku.php?id=software:fseventer:start

If you use Lion

Mobile Time Machine

Local disk space will be used, intelligently — never so much to cause an alert from the system. If you're curious, you can run two commands in Terminal:

man mtmd

q

tail -f /private/var/log/system.log | grep -E 'backup|mtm'

— set that Terminal window aside, leave it in background, work normally for an hour or so. What's logged should reassure you. When satisfied/finished, bring the Terminal window to foreground then to interrupt the running command:

controlc

FileVault 1 in Snow Leopard or Lion

In more modern versions of the operating system, use of bands for FileVault 1 should be not problematic. AFAIR space is freed dynamically, without the need to log out.

Whether free space was as well managed with FileVault 1 two years ago, when the question was posted, I can't recall.

Did you then use Leopard, or Snow Leopard?

Real time visualisation of file system activity

fseventer

http://fernlightning.com/doku.php?id=software:fseventer:start

If you use Lion

Mobile Time Machine

Local disk space will be used, intelligently — never so much to cause an alert from the system. If you're curious, you can run two commands in Terminal:

man mtmd

q

tail -f /private/var/log/system.log | grep -E 'backup|mtm'

— set that Terminal window aside, leave it in background, work normally for an hour or so. What's logged should reassure you. When satisfied/finished, bring the Terminal window to foreground then to interrupt the running command:

controlc

FileVault 1 in Snow Leopard or Lion

In more modern versions of the operating system, use of bands for FileVault 1 should be not problematic. AFAIR space is freed dynamically, without the need to log out.

Whether free space was as well managed with FileVault 1 two years ago, when the question was posted, I can't recall.

Did you then use Leopard, or Snow Leopard?

Real time visualisation of file system activity

fseventer

http://fernlightning.com/doku.php?id=software:fseventer:start

If you use Lion

Mobile Time Machine

Local disk space will be used, intelligently — never so much to cause an alert from the system. If you're curious, you can run two commands in Terminal:

man mtmd

q

tail -f /private/var/log/system.log | grep -E 'backup|mtm'

— set that Terminal window aside, leave it in background, work normally for an hour or so. What's logged should reassure you. When satisfied/finished, bring the Terminal window to foreground then to interrupt the running command:

controlc

FileVault 1 in Snow Leopard or Lion

In more modern versions of the operating system, use of bands for FileVault 1 should be not problematic. AFAIR space is freed dynamically, without the need to log out.

Whether free space was as well managed with FileVault 1 two years ago, when the question was posted, I can't recall.

Comments on FileVault 1 in Leopard, Snow Leopard and Lion. Not to be confused with FileVault 2.
Source Link
Graham Perrin
Graham Perrin
  • 7.8k
  • 14
  • 83
  • 246

Real time visualisation of file system activity

fseventer

http://fernlightning.com/doku.php?id=software:fseventer:start

If you use Lion

Mobile Time Machine

Local disk space will be used, intelligently — never so much to cause an alert from the system. If you're curious, you can run two commands in Terminal:

man mtmd

q

tail -f /private/var/log/system.log | grep -E 'backup|mtm'

— set that Terminal window aside, leave it in background, work normally for an hour or so. What's logged should reassure you. When satisfied/finished, bring the Terminal window to foreground then to interrupt the running command:

controlc

FileVault 1 in Snow Leopard or Lion

In more modern versions of the operating system, use of bands for FileVault 1 should be not problematic. AFAIR space is freed dynamically, without the need to log out.

Whether free space was as well managed with FileVault 1 two years ago, when the question was posted, I can't recall.

Did you then use Leopard, or Snow Leopard?

Real time visualisation of file system activity

fseventer

http://fernlightning.com/doku.php?id=software:fseventer:start

If you use Lion

Mobile Time Machine

Local disk space will be used, intelligently. If you're curious, in Terminal:

man mtmd

q

tail -f /private/var/log/system.log | grep -E 'backup|mtm'

— set that Terminal window aside, leave it in background, work normally for an hour or so. What's logged should reassure you. When satisfied/finished, bring the Terminal window to foreground then to interrupt the running command:

controlc

Real time visualisation of file system activity

fseventer

http://fernlightning.com/doku.php?id=software:fseventer:start

If you use Lion

Mobile Time Machine

Local disk space will be used, intelligently — never so much to cause an alert from the system. If you're curious, you can run two commands in Terminal:

man mtmd

q

tail -f /private/var/log/system.log | grep -E 'backup|mtm'

— set that Terminal window aside, leave it in background, work normally for an hour or so. What's logged should reassure you. When satisfied/finished, bring the Terminal window to foreground then to interrupt the running command:

controlc

FileVault 1 in Snow Leopard or Lion

In more modern versions of the operating system, use of bands for FileVault 1 should be not problematic. AFAIR space is freed dynamically, without the need to log out.

Whether free space was as well managed with FileVault 1 two years ago, when the question was posted, I can't recall.

Did you then use Leopard, or Snow Leopard?

Source Link
Graham Perrin
Graham Perrin
  • 7.8k
  • 14
  • 83
  • 246