Apple’s Slow Time Machine

Discussion in 'NZ Computing' started by Lawrence D'Oliveiro, Sep 29, 2010.

  1. This guy has done an analysis of performance problems with Apple’s much-
    vaunted “Time Machine†backup system
    <http://www.zdnet.com/blog/storage/why-time-machine-is-broken/1097>. Turns
    out it depends heavily on making and breaking hard links, which are usually
    cheap operations on *nix filesystems. Unfortunately, HFS+ is not such a
    filesystem; each such operation requires locking entire B-trees, which means
    blocking other operations, slowing everything down.

    I have rsync doing the same sort of thing (--link-dest) under Linux, running
    3 times a day, backing up over half a terabyte of user files. Each run takes
    only about a quarter of an hour.
    Lawrence D'Oliveiro, Sep 29, 2010
    #1
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  2. Lawrence D'Oliveiro

    Another Me Guest

    On 30/09/10 1:00 AM, Lawrence D'Oliveiro wrote:

    > I have rsync doing the same sort of thing (--link-dest) under Linux, running
    > 3 times a day, backing up over half a terabyte of user files. Each run takes
    > only about a quarter of an hour.


    Time machine is a home user solution, if you have half a terabyte of new
    user data three times a day to backup, chances are you aren't a home user.
    Another Me, Sep 29, 2010
    #2
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  3. In message <i80ad6$qga$>, Another Me wrote:

    > Time machine is a home user solution ...


    Wonder why home users are suffering performance problems, then?
    Lawrence D'Oliveiro, Sep 30, 2010
    #3
  4. Lawrence D'Oliveiro

    victor Guest

    On 30/09/2010 8:59 p.m., Lawrence D'Oliveiro wrote:
    > In message<i80ad6$qga$>, Another Me wrote:
    >
    >> Time machine is a home user solution ...

    >
    > Wonder why home users are suffering performance problems, then?


    I read the article and it says casual Mac users are fine with Time Machine

    Did you get that far ?
    victor, Sep 30, 2010
    #4
  5. In message <i81kmq$krb$-september.org>, victor wrote:

    > On 30/09/2010 8:59 p.m., Lawrence D'Oliveiro wrote:
    >
    >> In message<i80ad6$qga$>, Another Me wrote:
    >>
    >>> Time machine is a home user solution ...

    >>
    >> Wonder why home users are suffering performance problems, then?

    >
    > I read the article and it says casual Mac users are fine with Time Machine


    How did we suddenly get from “home†to “casual†users?

    > Did you get that far ?


    The question is, did you
    <http://www.zdnet.com/blog/storage/why-time-machine-is-broken/1097>:

    People I support here in “the real America†started complaining about
    Time Machine’s impact on performance. Spinning beach balls, long pauses,
    even system crashes.

    ...

    But if you receive and keep a lot of e-mail, download and keep a lot of
    content or perform large-file I/O intensive work - video, Photoshop,
    music - you’ll find that Time Machine has a noticeable and perhaps
    unacceptable impact on system performance.

    Seems like that description would apply to a lot of Mac users, given its
    much-vaunted target demographic.
    Lawrence D'Oliveiro, Sep 30, 2010
    #5
  6. Lawrence D'Oliveiro

    Another Me Guest

    On 30/09/10 8:59 PM, Lawrence D'Oliveiro wrote:
    > In message<i80ad6$qga$>, Another Me wrote:
    >
    >> Time machine is a home user solution ...

    >
    > Wonder why home users are suffering performance problems, then?


    I'm not sure, my machines backup to a drive off an Airport Express
    using time machine though the day and it happens in the background, I
    don't notice any performance issue when it is happening
    Another Me, Sep 30, 2010
    #6
  7. Lawrence D'Oliveiro

    Another Me Guest

    On 30/09/10 11:10 PM, Lawrence D'Oliveiro wrote:

    > People I support here in “the real America†started complaining about
    > Time Machine’s impact on performance. Spinning beach balls, long pauses,
    > even system crashes.


    Like I said, I haven't noticed any of those with Time Machine, I have
    just kicked off a backup and can't notice any performance issues at all.
    Now Safari is a different matter, but not time machine.



    > But if you receive and keep a lot of e-mail, download and keep a lot of
    > content or perform large-file I/O intensive work - video, Photoshop,
    > music - you’ll find that Time Machine has a noticeable and perhaps
    > unacceptable impact on system performance.
    >
    > Seems like that description would apply to a lot of Mac users, given its
    > much-vaunted target demographic.


    Actually Apples target demographic are people that can afford their
    machines, and the seem to target them quite well. The majority of the
    Photoshop users will be businesses, and they won't be using time machine
    as a backup. Now for the people who have purchased a lot of digital
    downloaded movies, this will only be backed up by Time Machine the once,
    it generally doesn't change so won't need backed up again.

    Now, have you actually ever used Time Machine?

    It is far from the perfect product, but it provides a quick, and easy
    solution for a home user to backup their machine.
    Another Me, Sep 30, 2010
    #7
  8. Lawrence D'Oliveiro

    victor Guest

    On 30/09/2010 11:10 p.m., Lawrence D'Oliveiro wrote:
    > In message<i81kmq$krb$-september.org>, victor wrote:
    >
    >> On 30/09/2010 8:59 p.m., Lawrence D'Oliveiro wrote:
    >>
    >>> In message<i80ad6$qga$>, Another Me wrote:
    >>>
    >>>> Time machine is a home user solution ...
    >>>
    >>> Wonder why home users are suffering performance problems, then?

    >>
    >> I read the article and it says casual Mac users are fine with Time Machine

    >
    > How did we suddenly get from “home†to “casual†users?
    >

    Same thing to me, casual means not intensive.
    Lets face it, everybody complains about how long backups take, this
    journalist/blogger/whatever is nothing new.
    Time machine works in the background for home users.
    Mac users who want to use rsync can do that too.
    victor, Sep 30, 2010
    #8
  9. In message <i82qih$nll$-september.org>, victor wrote:

    > Time machine works in the background for home users.


    Not very well, judging from the original article.

    Just to be clear: Time Machine’s use of hard links is not in itself a bad
    technique—rsync does the same sort of thing, and scales nicely to
    industrial-strength loads thereby. The problem is that Time Machine is let
    down by the Mac OS—that is where the limitation lies.
    Lawrence D'Oliveiro, Oct 3, 2010
    #9
  10. Lawrence D'Oliveiro

    victor Guest

    On 3/10/2010 11:34 p.m., Lawrence D'Oliveiro wrote:
    > In message<i82qih$nll$-september.org>, victor wrote:
    >
    >> Time machine works in the background for home users.

    >
    > Not very well, judging from the original article.
    >


    Experienced Mac users on this group say it works well.
    victor, Oct 3, 2010
    #10
  11. In message <i8apff$uht$-september.org>, victor wrote:

    > On 3/10/2010 11:34 p.m., Lawrence D'Oliveiro wrote:
    >
    >> In message<i82qih$nll$-september.org>, victor wrote:
    >>
    >>> Time machine works in the background for home users.

    >>
    >> Not very well, judging from the original article.

    >
    > Experienced Mac users on this group say it works well.


    Maybe it’s because they don’t know any better. They don’t realize that, if
    you have 100GB of data of which only a few gigs has changed since the last
    backup, it should only take a few minutes to find and copy those changes;
    they’re accustomed to it taking hours to complete.
    Lawrence D'Oliveiro, Oct 4, 2010
    #11
  12. Lawrence D'Oliveiro

    victor Guest

    On 4/10/2010 3:00 p.m., Lawrence D'Oliveiro wrote:
    > In message<i8apff$uht$-september.org>, victor wrote:
    >
    >> On 3/10/2010 11:34 p.m., Lawrence D'Oliveiro wrote:
    >>
    >>> In message<i82qih$nll$-september.org>, victor wrote:
    >>>
    >>>> Time machine works in the background for home users.
    >>>
    >>> Not very well, judging from the original article.

    >>
    >> Experienced Mac users on this group say it works well.

    >
    > Maybe it’s because they don’t know any better.


    Maybe it works well.
    victor, Oct 4, 2010
    #12
  13. In message <i8bcvs$426$-september.org>, victor wrote:

    > Maybe it works well.


    Maybe it’s because they don’t know any better. They don’t realize that, if
    you have 100GB of data of which only a few gigs has changed since the last
    backup, it should only take a few minutes to find and copy those changes;
    they’re accustomed to it taking hours to complete.
    Lawrence D'Oliveiro, Oct 4, 2010
    #13
  14. Lawrence D'Oliveiro

    David Empson Guest

    Re: Apple's Slow Time Machine

    Lawrence D'Oliveiro <_zealand> wrote:

    > In message <i8apff$uht$-september.org>, victor wrote:
    >
    > > On 3/10/2010 11:34 p.m., Lawrence D'Oliveiro wrote:
    > >
    > >> In message<i82qih$nll$-september.org>, victor wrote:
    > >>
    > >>> Time machine works in the background for home users.
    > >>
    > >> Not very well, judging from the original article.

    > >
    > > Experienced Mac users on this group say it works well.

    >
    > Maybe it's because they don't know any better. They don't realize that, if
    > you have 100GB of data of which only a few gigs has changed since the last
    > backup, it should only take a few minutes to find and copy those changes;
    > they're accustomed to it taking hours to complete.


    Um, what?

    The only time I've seen Time Machine taking "hours" to complete a backup
    is when it is doing its initial backup, on a computer with a large
    number of files, so it is having to copy everything.

    I use Time Machine to backup up my laptop to an external Firewire hard
    drive. It typically takes less than two minutes to back up everything
    which changed since the last backup, which is a tiny proportion of the
    total number of files on the source volume. Total size of files on my
    source volume is about 250 GB, and the total file count is in the order
    of several hundred thousand.

    If I've done something like install a system update, the next backup
    takes somewhat longer (because a lot more files changed), but still only
    a few minutes. My first backup today (catching up from Thursday) took
    less than 5 minutes to back up 3 GB, and another 2 minutes to purge
    several hourly backups from last week. The next hourly backup took less
    than a minute (very little had changed).

    I don't even notice it doing a backup unless I listen to the hard drive
    or see the spinning Time Machine indicator in the menu bar.

    --
    David Empson
    David Empson, Oct 4, 2010
    #14
  15. In message <i81qfe$lv4$>, Another Me wrote:

    > The majority of the Photoshop users will be businesses, and they won't be
    > using time machine as a backup.


    What will they be using, pray tell?

    > Now for the people who have purchased a lot of digital downloaded movies,
    > this will only be backed up by Time Machine the once, it generally doesn't
    > change so won't need backed up again.


    That’s where the problem comes in. The way Time Machine avoids making
    multiple copies of unchanged files is by putting in hard links to the
    existing copies.

    This making and breaking of hard links is a common operation on Unix/Linux
    systems, so most Unix/Linux filesystems are designed to ensure it’s cheap to
    perform. Not, however, the HFS+ filesystem which is Apple’s preferred
    filesystem under MacOS. That’s where the performance problems with Time
    Machine come from.

    Read the article
    <http://www.zdnet.com/blog/storage/why-time-machine-is-broken/1097> for more
    info on this.
    Lawrence D'Oliveiro, Oct 5, 2010
    #15
  16. Re: Apple's Slow Time Machine

    In message <1jpufdf.1hfyp181eb0telN%>, David Empson
    wrote:

    > I don't even notice it doing a backup unless I listen to the hard drive
    > or see the spinning Time Machine indicator in the menu bar.


    Sounds like you’re not doing much else with the hard drive at the same time.

    The problem arises because it has to lock various entire filesystem B-trees
    while creating and inserting hard links. On its own this may not matter
    much, but if other processes are performing concurrent operations on the
    filesystem, they will be blocked by these locks. Or conversely, if they get
    in first, they will hold up the Time Machine processes.

    More details here
    <http://www.zdnet.com/blog/storage/why-time-machine-is-broken/1097>.
    Lawrence D'Oliveiro, Oct 8, 2010
    #16
  17. Lawrence D'Oliveiro

    David Empson Guest

    Re: Apple's Slow Time Machine

    Lawrence D'Oliveiro <_zealand> wrote:

    > In message <1jpufdf.1hfyp181eb0telN%>, David Empson
    > wrote:
    >
    > > I don't even notice it doing a backup unless I listen to the hard drive
    > > or see the spinning Time Machine indicator in the menu bar.

    >
    > Sounds like you're not doing much else with the hard drive at the same time.


    Normal use patterns. I can't tell that a backup is occurring, even if
    I'm doing something with a moderate amount of disk activity.

    Something needing heavy disk activity will be impacted due to the
    overhead of Time Machine copying data, etc., but Time Machine's backupd
    runs at lower priority than normal to mitigate this somewhat.

    If you are doing something important and time critical with lots of disk
    I/O, you should turn off Time Machine during that task. If that is a
    regular requirement then you should be looking at a different backup
    solution, or using Time Machine with some kind of scheduling tool.

    > The problem arises because it has to lock various entire filesystem B-trees
    > while creating and inserting hard links.


    On the backup drive? So what? I'm only using that drive for backups, so
    a file system lock will only delay the backup. I don't notice any impact
    on file I/O on the main drive (apart from data copying).

    It is not a good idea to use the Time Machine backup volume for other
    things, because Time Machine is designed to (eventually) completely fill
    the volume, which won't leave you space for other files.

    You can manipulate this behaviour by partitioning a drive or setting up
    disk images to reserve space for Time Machine or other uses, in which
    case I expect any file system locking is only going to affect the
    partition or disk image in which Time Machine is operating.

    > On its own this may not matter much, but if other processes are performing
    > concurrent operations on the filesystem, they will be blocked by these
    > locks. Or conversely, if they get in first, they will hold up the Time
    > Machine processes.
    >
    > More details here
    > <http://www.zdnet.com/blog/storage/why-time-machine-is-broken/1097>.


    Yes, I read it already. Most of it doesn't seem to agree with my
    observed reality, nor that of anyone else I know who is using Time
    Machine.

    The only signficant point I agree with is that Time Machine doesn't cope
    well with multi-gigabyte files that have small changes, as it needs to
    back up the entire file again.

    There are ways around that problem as well: things like Entourage
    databases (single file containing all of your e-mail) and virtual hard
    drives for VMs can be set up inside a sparse bundle disk image, which is
    implemented as a folder containing lot of "band" files of a few
    megabytes each. A localised change will only affect a few of the bands,
    so only the changed parts need to be backed up again.

    --
    David Empson
    David Empson, Oct 8, 2010
    #17
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