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Problem w/ DST - file time stamps change (Read 11,516 times)
Mar 15th, 2007 at 7:40pm

Druidia   Offline
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This is the second time I've encountered this problem.  The first was last year when we moved the clock back and now when we moved the clock ahead. 

Background info:
I synchronize my laptop with an external HD.  Last weekend, the notebook  clock automatically got updated/changed to an hour ahead (I know I can set it back manually but was hoping there's a less primitive solution). Since the clock changed, the time stamps of all the files in my computer also got adjusted of course.

Problem description:
Since the time stamps on all my laptop files have been changed, when I did a scan, all the files came as out as "Newer."

Question:
How do I scan for newer files and disregard time stamp changes that's just due to DST?  When this happened to me last year, I had to go the long way and manually change the time on my laptop so I can update authentically new files.  Did several switching/checking back and forth just to make sure I didn't miss a file.  I was hoping there's an easier and less primitive way of going around this DST problem (since I'll have to do this twice a year, every year).
 
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Reply #1 - Mar 16th, 2007 at 12:12am

Daniel   Offline
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Quote:
This is the second time I've encountered this problem.  The first was last year when we moved the clock back and now when we moved the clock ahead.  

Background info:
I synchronize my laptop with an external HD.  Last weekend, the notebook  clock automatically got updated/changed to an hour ahead (I know I can set it back manually but was hoping there's a less primitive solution). Since the clock changed, the time stamps of all the files in my computer also got adjusted of course.

Problem description:
Since the time stamps on all my laptop files have been changed, when I did a scan, all the files came as out as "Newer."

Question:
How do I scan for newer files and disregard time stamp changes that's just due to DST?  When this happened to me last year, I had to go the long way and manually change the time on my laptop so I can update authentically new files.  Did several switching/checking back and forth just to make sure I didn't miss a file.  I was hoping there's an easier and less primitive way of going around this DST problem (since I'll have to do this twice a year, every year).


Hello,

Strange issue. Seems like your Desktop computer updates DST, but your notebook not. DST is commanded by Windows, not by Comparator Fast. If you want, you may specify a higher threshold (on Scan Parameters) based on time difference: 3600 for one hour (+) or -3600 for each hour (-).

Regards,

Daniel  Cheesy
 
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Reply #2 - Mar 16th, 2007 at 11:22am

Druidia   Offline
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Hello,

Strange issue. Seems like your Desktop computer updates DST, but your notebook not. DST is commanded by Windows, not by Comparator Fast. If you want, you may specify a higher threshold (on Scan Parameters) based on time difference: 3600 for one hour (+) or -3600 for each hour (-).

Regards,

Daniel  Cheesy


I said I synchronize my laptop with an external HD.  I didn't say I synchronize my laptop with a desktop computer.  If I'm synchronizing my laptop with a desktop computer then I wouldn't have this problem since, of course, the desktop computer's clock would also be automatically updated.

As I'm pretty sure there are many other people who have external HDs (not the internal HDs inside their desktop computers), I was wondering what they do to get around this DST problem.



 
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Reply #3 - Mar 16th, 2007 at 11:55am

Druidia   Offline
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If you want, you may specify a higher threshold (on Scan Parameters) based on time difference: 3600 for one hour (+) or -3600 for each hour (-).

Regards,

Daniel  Cheesy


Specifying 3600 in time threshold didn't work.   CF still detected the several thousands of files in my laptop as "newer."

You can't type in or input by clicking on the down button a negative value (i.e., -3600) in time threshold.
 
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Reply #4 - Mar 16th, 2007 at 5:09pm

Druidia   Offline
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I also tried solving this problem by doing the same thing I did the first time I had this problem last year.

  • Disabled "Automatically adjust  clock for daylight saving changes" in my laptop so I can synchronize the "authentic new files" in my laptop with my external HD.
  • Ran CF and synchronized "authentic new files" in my laptop with my external HD.
  • Enabled "automatically adjust clock for daylight saving changes" in my laptop.
  • Ran CF again.  As expected, CF detected all the files in my laptop as "New."
    Selected all the files in my laptop (source) and clicked "Touch selected files as older." 


The problem with choosing this route "Touch selected files as older" is that it doesn't always work.  I've touched the files as older and yet when I do a rescan, it still detects all those files as "new."  It's really tedious to keep repeating "touch files as older-scan" route because, since I'm dealing with thousands of files, the scanning takes a really really long time.
 
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Reply #5 - Mar 16th, 2007 at 7:29pm

Daniel   Offline
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Specifying 3600 in time threshold didn't work.   CF still detected the several thousands of files in my laptop as "newer."

You can't type in or input by clicking on the down button a negative value (i.e., -3600) in time threshold.


Hello,

Doesn't need to include a negative value... the same value works as difference for both files (if you specify 3600 -must be 3602 to avoid the 2 second difference explained in Help- it works as 3600 seconds of difference between files). What's the time difference of the files shown as newer?

Daniel  Smiley
 
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Reply #6 - Mar 16th, 2007 at 7:38pm

Daniel   Offline
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I said I synchronize my laptop with an external HD.  I didn't say I synchronize my laptop with a desktop computer.  If I'm synchronizing my laptop with a desktop computer then I wouldn't have this problem since, of course, the desktop computer's clock would also be automatically updated.

As I'm pretty sure there are many other people who have external HDs (not the internal HDs inside their desktop computers), I was wondering what they do to get around this DST problem.





Hello again,

You´re right, you mentioned external HD  Roll Eyes, sorry for the error.

I received once a post about sync an external disk, using threshold apparently works (if the time difference is one hour between the "newer" files, please remember to specify two more seconds, I mean, 3602).

I think this may be a new feature for a future release, I need to think more about this. Certainly is a problem having an external disk out of sync. How to distinguish or stablish the difference between an internal (always online) disk and an external (usually offline) disk? This may require a one-time user intervention, just like you do. Let me think more about this. If you have a suggestion, please let me know.

Regards,

Daniel  Cheesy
 
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Reply #7 - Mar 16th, 2007 at 8:04pm

Daniel   Offline
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I also tried solving this problem by doing the same thing I did the first time I had this problem last year.

  • Disabled "Automatically adjust  clock for daylight saving changes" in my laptop so I can synchronize the "authentic new files" in my laptop with my external HD.
  • Ran CF and synchronized "authentic new files" in my laptop with my external HD.
  • Enabled "automatically adjust clock for daylight saving changes" in my laptop.
  • Ran CF again.  As expected, CF detected all the files in my laptop as "New."
    Selected all the files in my laptop (source) and clicked "Touch selected files as older."  


The problem with choosing this route "Touch selected files as older" is that it doesn't always work.  I've touched the files as older and yet when I do a rescan, it still detects all those files as "new."  It's really tedious to keep repeating "touch files as older-scan" route because, since I'm dealing with thousands of files, the scanning takes a really really long time.


Hello,

I ran CF on the test system, comparing with a Pen drive (I need to prepare a more elaborated test with external disk). Once changed DST (1 hour), the files on Pen drive appears as newer. I have two options:

1) Just do a copy/update, if I am sure the files are the same, so this ensures the next scans will works with DST fixed on external.

2) Using threshold (I used 3600 and 3602, both worked fine). Then I selected all items, and used the "Touch as" command (in my test, as older), both worked fine with more than 2000 files. You mentioned problems with the "Touch as" function, please send an email to support describing your problem, in order to revise this, to ensure is not a bug. Please let me know what kind of files are not touched (system files, read only, compressed).

The comparison speed concerning external devices depends on the speed of the devices and port used. If you are using an external USB disk with an USB 1.1 port, I highly recommends you to upgrade your hardware to USB 2.0.

Regards,

Daniel  Cheesy
 
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Reply #8 - Mar 16th, 2007 at 8:15pm

Druidia   Offline
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Hello again,

You´re right, you mentioned external HD  Roll Eyes, sorry for the error.

I received once a post about sync an external disk, using threshold apparently works (if the time difference is one hour between the "newer" files, please remember to specify two more seconds, I mean, 3602).

I think this may be a new feature for a future release, I need to think more about this. Certainly is a problem having an external disk out of sync. How to distinguish or stablish the difference between an internal (always online) disk and an external (usually offline) disk? This may require a one-time user intervention, just like you do. Let me think more about this. If you have a suggestion, please let me know.

Regards,

Daniel  Cheesy


Here's an update about my reply#4 above.
As I said, the Touch Files as Older doesn't work because when I rescan, CF still detects the files as newer.  And even if this works, this isn't really a good solution.  Why? Because, when you're dealing with 40,000+ files, CF then hogs all my computer's resources. 

I remember that what happened last year was that, after trying out the method above and finding that it didn't work, I just set aside a weekend to delete everything in the external HD and freshly transfer everything from my internal to the internal HD.  I'm not looking forward to having to do this twice a year.

Back to the basics of the problem:
  • When there's a DST changeover, computers automatically updates the displayed time stamp.  In reality, the original timestamps of the files do not change.
  • The displayed time stamps of files in the external HD do not change.  I don't think this will change even if the external HD is hooked up to my laptop at the time of the DST changeover.  Or would it have changed?


I'm not a computer programmer so all I can do is ask you if any of these are possible:
  • Can CF be modified so that it sees the original time stamp of files in the internal HD?  I'm thinking this could be possible because the laptop doesn't really change the original time stamp. Right?  All it changes is the way the time stamp is displayed (an hour ahead or an hour back).  If it sees the original time stamp then it won't see any change in the time stamps of files in the internal and the external HD (since the external HD files will alway bear the original time stamp).
  • Can CF be modified so that it has a feature that allows time stamp display in the target HD to be manually adjusted with DST changes?

 
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Reply #9 - Mar 16th, 2007 at 8:29pm

Druidia   Offline
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Posts: 14
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Quote:
Hello,

I ran CF on the test system, comparing with a Pen drive (I need to prepare a more elaborated test with external disk). Once changed DST (1 hour), the files on Pen drive appears as newer. I have two options:

1) Just do a copy/update, if I am sure the files are the same, so this ensures the next scans will works with DST fixed on external.


True, I can do this but this isn't a permanent solution. This still means I would have to do this twice a year.  It's also not a good solution because having to copy/update 40,000+ files takes a long, long time.  That's no different from me just copying everything manually to my external HD without using CF.

Quote:
2) Using threshold (I used 3600 and 3602, both worked fine). Then I selected all items, and used the "Touch as" command (in my test, as older), both worked fine with more than 2000 files. You mentioned problems with the "Touch as" function, please send an email to support describing your problem, in order to revise this, to ensure is not a bug. Please let me know what kind of files are not touched (system files, read only, compressed).


I already did the Touch files as older option. 

Here are more details of what happened;

  • Touched files in internal HD as older.  Had to do this twice before they didn't come up as "new" anymore after rescanning with CF.
  • After doing above step, internal HD files didn't come up as newer BUT the external HD files did!  Cheesy Now this is almost so funny if I didn't have to spend so much time doing this over and over again.
  • Did a scan again and, as before, external HD files are now coming up as "new".  So I selected them and touched them as older.  Did this twice.  External HD files still came up as "new."
  • Methinks I will be going around in circles with this touch file as older approach.  And it does take a really long time to just select (not including touching up) 40,000+ files.  It hangs up my computer!
All kinds of files were not touched.  I did this twice.  I say they're not touched as older files because, when I did a rescan, they still came up as new.

Quote:
The comparison speed concerning external devices depends on the speed of the devices and port used. If you are using an external USB disk with an USB 1.1 port, I highly recommends you to upgrade your hardware to USB 2.0.


I am using USB 2.0.

It's 35 Gb of files that are being synchronized.  Normally, if I'm synchronizing daily, it doesn't take a long time to scan files (because it would be just less than a hundred to probably a little over a hundred files that would have to be updated).
However, with this DST problem, CF now has to scan 35 GB worth of files.  That's why it's taking so long.
 
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Reply #10 - Mar 17th, 2007 at 11:39am

Daniel   Offline
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Hello,

Quote:
I already did the Touch files as older option.   

Here are more details of what happened;


Touched files in internal HD as older.  Had to do this twice before they didn't come up as "new" anymore after rescanning with CF.

After doing above step, internal HD files didn't come up as newer BUT the external HD files did!   Now this is almost so funny if I didn't have to spend so much time doing this over and over again.

I'm still don't understand why you have to repeat the Touch process, the first pass didn't work for you? Is there an error reported on Log?

And the behavior you described is not normal, once a file is correctly touched, both files have the same Modified Date/Time. Is there a chance the threshold parameter was 3602 when you repeated the comparison?

Quote:
All kinds of files were not touched.  I did this twice.  I say they're not touched as older files because, when I did a rescan, they still came up as new.

I try to determinate the reason. Maybe checking the log (in debug mode) will help to determine why some files on your hard drive are not touched (security settings? -owner-).


Quote:
I am using USB 2.0.

It's 35 Gb of files that are being synchronized.  Normally, if I'm synchronizing daily, it doesn't take a long time to scan files (because it would be just less than a hundred to probably a little over a hundred files that would have to be updated).
However, with this DST problem, CF now has to scan 35 GB worth of files.  That's why it's taking so long.

USB 2.0 is the best. Using 1.1 with an external device is just a nightmare (extremely slow) to simple copy procedures (specially if big files involved).

I scanned 74GB of files on an old Athlon XP 2.4GHz, with 512MB of RAM, and adding more than 40,000 items on  results list will slow down the process (is a normal behavior), but if this hogs your system resources, you may need to tune your XP system (I guess is XP), specially the memory assigned to Cache files and ensure your CPU's cache is configured, this helps a lot. Another tip is disable the "Last Accessed" date/time control in Windows.

SOLUTION

After some tests and simulations, I think the best schema to solve this DST issue is including an option in CF (Comparator Fast) to handle DST: when comparing two files by Date/Time, accept the files as "in sync" if the time difference is exactly one hour and if both files have the same size. This is the more faster solution with no user intervention.

Actually, I prefer the Touch solution because looking two files with different time as "same" can be confused (specially if other person have access to your files, may be other's Users case).

This option will be including on next release 1.0.0.27.

Take care,

Daniel  Cheesy
 
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Reply #11 - Mar 26th, 2007 at 7:21pm

Daniel   Offline
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Druidia wrote on Mar 15th, 2007 at 7:40pm:
This is the second time I've encountered this problem.  The first was last year when we moved the clock back and now when we moved the clock ahead.  

Background info:
I synchronize my laptop with an external HD.  Last weekend, the notebook  clock automatically got updated/changed to an hour ahead (I know I can set it back manually but was hoping there's a less primitive solution). Since the clock changed, the time stamps of all the files in my computer also got adjusted of course.

Problem description:
Since the time stamps on all my laptop files have been changed, when I did a scan, all the files came as out as "Newer."

Question:
How do I scan for newer files and disregard time stamp changes that's just due to DST?  When this happened to me last year, I had to go the long way and manually change the time on my laptop so I can update authentically new files.  Did several switching/checking back and forth just to make sure I didn't miss a file.  I was hoping there's an easier and less primitive way of going around this DST problem (since I'll have to do this twice a year, every year).


Hello,

New release of Comparator Fast for Windows now include Automatic DST (Options|Preferences|DST).

Take care,

Daniel  Cheesy
 
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