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Windows Standby RAM + Verify that files are copied correctly

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fls
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Windows Standby RAM + Verify that files are copied correctly

Post by fls »

My system sometimes flips a bit and the destination files from a simple explorer file copy becomes corrupt.
I don't know what causes it but until I track down the error I want to be sure the files written with Sync Back Pro are 100% non corrupted.

So now my questions/concern:
How does SyncBackPro make sure the destination files in a copy is written correctly and not just read from Windows Standby RAM on the hash check?

I switch the option "Verify that files are copied correctly" on and see that the file is read back right after its written - but doesn't the file get read from Windows Standby RAM instead of the destination hard drive?

Because i've noticed that files are read from Windows Standby RAM if they still reside there when I'm not using SyncBackPro. And only a reboot makes sure that I afterwards read the file from the destination hard disk and not Windows Standby RAM.
Conrad Chung
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Re: Windows Standby RAM + Verify that files are copied corre

Post by Conrad Chung »

Hash values are computed to produce a unique value based on the contents of a file. We use these values to check if a file contents is the same or different from another.

For disk-to-disk transfers, we use MD5 algorithm to generate the hash. (if Zips are involved, we use CRC32 as that is all that is stored in Zips).
fls
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Re: Windows Standby RAM + Verify that files are copied corre

Post by fls »

ok but how does SyncBackPro make sure that it reads back the file from the destination HD for hash checking and not just the cashed one in windows standby ram?

I've noticed that SyncBackPro doesn't seem to flush windows standby ram of the cached file after the filecopy process so that/those files are still in memory and windows often chooses to read from memory instead of the HD if the file/files is still there.

I've got 32 GB of memory so alot of files are residing in that before they get overwritten by newer ones.

You can use this program to see what files are residing in the windows standby ram and use the menu to 'empty standby list' which clears all files from memory and forces a read from the HD
http://technet.microsoft.com/en-us/sysi ... 00229.aspx
fls
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Re: Windows Standby RAM + Verify that files are copied corre

Post by fls »

I've done a bit more testing with a 100 GB backup.

Source = HD1
Destination = HD2

I monitored the Disk acces with Windows Resource Monitor while the backup was running and I saw reads from HD1 and writes to HD2 but no reads from HD2.

Then while the backup was still running I tried continually (every few secounds) to clear the Windows Standby RAM with the microsoft util RAM MAP http://technet.microsoft.com/en-us/sysi ... 00229.aspx for a period of about 1-2 minutes and then I suddenly started to see reads from HD2.

When I stopped clearing the Windows standby memory the reads from HD2 faded out and stopped again.

The problem for me is that the corruption of files happens on the written files on the destination HD2 in the write process and not in the read process from the source HD1.

So it seems like SyncBackPro in the verification process just uses the file from Windows Standby RAM and doesn't read back the file from the destination HD which then defeats the purpose of the check?
BMWBig6
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Re: Windows Standby RAM + Verify that files are copied corre

Post by BMWBig6 »

fls wrote:
Sun Nov 02, 2014 3:41 pm
So it seems like SyncBackPro in the verification process just uses the file from Windows Standby RAM and doesn't read back the file from the destination HD which then defeats the purpose of the check?
Is this still true (especially of Version 9)?
Swapna
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Re: Windows Standby RAM + Verify that files are copied correctly

Post by Swapna »

Hi,

You can tick the option 'Stop Windows from caching a files contents when it is copied' under: Modify profile > Expert > Copy/Delete > Advanced page, and then SyncBack will tell Windows not to cache the contents of the file in memory. But if the drive, network or anything else is caching then its beyond our control.

Thank you.
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