I'm a huge fan of Backup with verification, but I notice that the verification stage is quite slow, slower than the copy itself. On the other hand "Edit | Compare | Compare Current File with Previous File" is fast. It seems like "Edit | Compare" reads both files simultaneously, while the verification in Backup reads them separately, in chunks. But I may be very well wrong on this, yet the difference in speed is absolutely noticeable. Is there anything that can be done to speed up Backup's verification?
PS: I usually backup from an internal SSD to an external USB3 that can reach 100 MB/s write speed, yet verification lives in the 40 MB/s realm.
Faster verification in Backup, like in Edit | Compare
Faster verification in Backup, like in Edit | Compare
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Don sees all [cit. from viewtopic.php?p=124094#p124094]
Don sees all [cit. from viewtopic.php?p=124094#p124094]
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Re: Faster verification in Backup, like in Edit | Compare
Both Backup and Compare use Byte-To-Byte verification (if Backup is configured like this) with almost exactly the same code. The only differences:
a) Backup allows for more interception (DoEvents), so that you can freely drag the progress dialog or abort by ESC with immediate effect.
b) Backup's progress status is maybe a bit more work .
I think a) has to be the cause of the speed difference.
a) Backup allows for more interception (DoEvents), so that you can freely drag the progress dialog or abort by ESC with immediate effect.
b) Backup's progress status is maybe a bit more work .
I think a) has to be the cause of the speed difference.
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Re: Faster verification in Backup, like in Edit | Compare
I made some experiments: I was wrong. That's not the cause of it. It's interesting. Still searching...
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Re: Faster verification in Backup, like in Edit | Compare
Got it: The target file (that has just been written a millisecond ago) has to opened with FILE_FLAG_NO_BUFFERING to ensure all buffers are flashed to disk. This makes it slower. No way around this.
For max speed possible in verification ensure these tweaks are both zero:
For max speed possible in verification ensure these tweaks are both zero:
Code: Select all
CustomCopyFlags=0 (or more exactly: ensure it does not have bit COPY_FILE_NO_BUFFERING (4096))
CustomCopyNoBufferingFromBytes=0
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Re: Faster verification in Backup, like in Edit | Compare
I see... Those tweaks are already both to zero.
I did some more tests and yes, I can see that backup verification speed is consisten, while sometimes Compare is fast because it uses some cache. This probably tricked me.
Anyway, just to have some numbers, I did a comparison between two files, and crunched 536,188,936 bytes in 7.75 seconds = 65.98 MB/s. About 65% of the read speed of the slower drive. Do you get similar results?
I did some more tests and yes, I can see that backup verification speed is consisten, while sometimes Compare is fast because it uses some cache. This probably tricked me.
Anyway, just to have some numbers, I did a comparison between two files, and crunched 536,188,936 bytes in 7.75 seconds = 65.98 MB/s. About 65% of the read speed of the slower drive. Do you get similar results?
Tag Backup - SimpleUpdater - XYplorer Messenger - The Unofficial XYplorer Archive - Everything in XYplorer
Don sees all [cit. from viewtopic.php?p=124094#p124094]
Don sees all [cit. from viewtopic.php?p=124094#p124094]