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From: TaliesinSoft on 18 May 2010 12:40
On 2010-05-18 11:24:23 -0500, Richard Maine said:

> If you have 24 hourly backups right after having made one, then you
> can't recover from errors made 23.5 hours ago.

Methinks that is the needed "bonk" on the head! Many thanks!

--
James Leo Ryan
Austin, Texas

From: Matthew Russotto on 18 May 2010 23:26
In article <1jiojyl.mbpctzekzkkuN%nospam(a)see.signature>,
Richard Maine <nospam(a)see.signature> wrote:
>
>I thought I explained this, but I guess I failed to get the point
>across. This isn't just Time Machine. It is the nature of any data
>organization that includes point samples over a range. Having spent 40
>years of my career working with that general kind of data, it is pretty
>much second nature to me. I couldn't even point to where I learned it or
>what I learned it from, though I'm sure I wasn't born with the notion.
>Maybe it has become so "obvious" to me that I can't adequately explain
>it to someone who doesn't "just get it". It isn't exactly a complicated
>point, but I don't seem able to get it across.

I've often heard it described as the "fencepost problem" or a
"fencepost error" when done wrong -- if you have n sections of fence,
you need n+1 fenceposts.
--
The problem with socialism is there's always
someone with less ability and more need.
From: TaliesinSoft on 19 May 2010 00:09
On 2010-05-18 22:26:38 -0500, Matthew Russotto said:

> In article <1jiojyl.mbpctzekzkkuN%nospam(a)see.signature>,
> Richard Maine <nospam(a)see.signature> wrote:
>>
>> I thought I explained this, but I guess I failed to get the point
>> across. This isn't just Time Machine. It is the nature of any data
>> organization that includes point samples over a range. Having spent 40
>> years of my career working with that general kind of data, it is pretty
>> much second nature to me. I couldn't even point to where I learned it or
>> what I learned it from, though I'm sure I wasn't born with the notion.
>> Maybe it has become so "obvious" to me that I can't adequately explain
>> it to someone who doesn't "just get it". It isn't exactly a complicated
>> point, but I don't seem able to get it across.
>
> I've often heard it described as the "fencepost problem" or a
> "fencepost error" when done wrong -- if you have n sections of fence,
> you need n+1 fenceposts.

And, as the person initiating this thread, and as the person that had a
difficult time understanding why 25 hourly backups were required to
properly cover a 24 hour period, it was that "bonk on the head" that
somehow made me fully understand.

--
James Leo Ryan
Austin, Texas

From: TaliesinSoft on 20 May 2010 00:52
On 2010-05-19 16:36:15 -0500, Michelle Steiner said:

> In article <85fs2qFsp6U2(a)mid.individual.net>,
> TaliesinSoft <taliesinsoft(a)me.com> wrote:
>
>> Which takes us back to my original pondering as to why Time Machine
>> needs 25 consecutive hourly backups to identify the changes that have
>> occurred within the last 24 consecutive hours?
>
> It doesn't. Any 24-hour interval will contain 25 one-hour points,
> including the starting point and the ending point.

Michelle,

Yeserday it finally got to me, thanks to one of the respondents in this
thread, why it takes 25 consecutive hours of Time Machine postings to
include everything that has happened in the last 24 hours.

Jim

--
James Leo Ryan
Austin, Texas

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