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although ICE ECC reports "Recover is possible"...

 
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gumbert-gumbert



Joined: 15 Dec 2006
Posts: 4

PostPosted: Sat Dec 16, 2006 6:30 pm    Post subject: although ICE ECC reports "Recover is possible"... Reply with quote

i've tested ICE ECC 2.2.1 on some dummy rar archives.

and i've got some sombre results:

when i simply rewrite random blocks of bytes in a data file, that is change data file content only, with no block shift & no file size change - ICE ECC recovers such a crrupted archive perfectly.

but when i edit data file and Do block shift (even tiny one) & file size change, - although ICE ECC reports "Recover is possible", it ends up with "File write error", "Block write error" or sometimes "Internal error - " ... and nothing is recovered.

here's an example of ice log. ICE ECC 2.2.1 says:


Code:
Physical Memory - 511 MB
Memory Usage - 306 MB

Speed - 370.07 MB/Sec
Configuration - 1, 0, 4

Verify started: C:\temp;
Check - noname.ecc
Use ECC file - C:\temp\noname.ecc
Verify Data Files
Damaged block - 2
Damaged block - 3
...
Damaged block - 1022
Damaged block - 1023
File read error - C:\temp\noname.rar
Damaged block - 1024
Verify ECC Files
Search - noname.dat
Found block - 3
Found block - 4
...
Found block - 1023
Found block - 1024
Some files are damaged. Recover is possible
Copy files
Matrix calculation - 0
Recovery Data Files
File write error - C:\temp\noname.rar
Block write error - 2, A
Recover failed
Verify failed


"File read error" just before the last Damaged block - is the distinctive feature of every failed recovery log.

Can You fix it ?

i only ask You 'cause iceecc.chm says: "Both .ecc files and data files are immune to shift."

WinXP SP1. CPU, RAM and HDD are just fine.
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ICE Graphics
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Joined: 31 Mar 2003
Posts: 430

PostPosted: Sat Dec 16, 2006 9:44 pm    Post subject: Re: although ICE ECC reports "Recover is possible" Reply with quote

gumbert-gumbert wrote:
but when i edit data file and Do block shift (even tiny one) & file size change, - although ICE ECC reports "Recover is possible", it ends up with "File write error", "Block write error" or sometimes "Internal error - " ... and nothing is recovered.

How much recovery blocks there are in noname.ecc file ?
What the shift are you apply ?
The main problem what i see in recovery log: File write error. Is it write accessible to C:\temp\noname.rar ?
Do you have enought free space ? Shift search mode require free space on hdd twice large than data+ecc files size.
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gumbert-gumbert



Joined: 15 Dec 2006
Posts: 4

PostPosted: Sun Dec 17, 2006 6:28 pm    Post subject: Re: although ICE ECC reports "Recover is possible" Reply with quote


a). i took explorer.exe (1 004 032 bytes) (C:\WINDOWS\explorer.exe)
b). then i've packed it with WinRAR (with Default recovery record = 1%)
c). so i had explorer.rar (366 961 bytes)
d). i've created c:\temp and placed archive into it // so it's not read-only
// free space on system disk c: ~ 30 GB
e). ICE ECC 2.2.1 has generated explorer.ecc with Default settings:

Source block count: 717
Block size: 512

Redundancy: 1%
Number of recovery blocks: 7

Header Redundancy: 200%
Logarithmic: 50%

explorer.ecc passed full test

f). then i've started hex-editor and corrupted explorer.rar in this way:

attempt 2. data shift & No file size change
-----------------------------------------------
i've pasted 1 empty byte at offset 512 (decimal)
that is at position of the 1st byte of the 2nd virtual block

then at offset 1024 (the very end of the 2nd virtual block) i've removed 1 byte

so there was data/block shift and No file size change
only 2nd block is damaged

ICE ECC v2.2.1 says:

Physical Memory - 511 MB
Memory Usage - 306 MB

Speed - 369.11 MB/Sec
Configuration - 1, 0, 4

Verify started: C:\temp;
Check - explorer.ecc
Use ECC file - C:\temp\explorer.ecc
Verify Data Files
Damaged block - 2
Damaged block - 3
Damaged block - 4
...
Damaged block - 715
Damaged block - 716
Damaged block - 717
Wrong file size - C:\temp\explorer.rar
Verify ECC Files
Search - explorer.rar
Found block - 2
Found block - 3
Found block - 4
...
Found block - 715
Found block - 716
Found block - 717
Some files are damaged. Recover is possible
Copy files
Recovery Data Files
Finalization
All files succesfully recovered
Verify finished


as You can see, ICE ECC 2.2.1 is able to access and rewrite corrupted data file.
and there was No "File read/write error". nothing of the kind.



attempt 3. data shift & file size change
--------------------------------------------
again i've pasted 1 empty byte at offset 512 (decimal)

then i've removed the last 2 bytes of the 2nd virtual block

so there was data/block shift and file size is changed, decreased.
and again only 2nd block is damaged.


ICE ECC v2.2.1 says:

Physical Memory - 511 MB
Memory Usage - 306 MB

Speed - 370.07 MB/Sec
Configuration - 1, 0, 4

Verify started: C:\temp;
Check - explorer.ecc
Use ECC file - C:\temp\explorer.ecc
Verify Data Files
Damaged block - 2
Damaged block - 3
Damaged block - 4
...
Damaged block - 714
Damaged block - 715
Damaged block - 716
File read error - C:\temp\explorer.rar
Damaged block - 717
Verify ECC Files
Search - explorer.rar
Found block - 3
Found block - 4
Found block - 5
...
Found block - 714
Found block - 715
Found block - 716
Found block - 717
Some files are damaged. Recover is possible
Copy files
Matrix calculation - 0
Recovery Data Files
File write error - C:\temp\explorer.rar
Block write error - 2, A
Recover failed
Verify failed


Sad


next i've tried .ecc files with more recovery blocks:

as an example - explorer.ecc with 709 recovery blocks that is 99% redundancy.
and You know what, - it failed! same "Block write error - 2, A".

only explorer.ecc with exactly 717 recovery blocks that is 100%-redundancy has managed to cope with a task ... despite the fact that there was, THERE WAS ! "File read error" too.

but 100% (in fact, more than 170% because of header redundancy) is just too much...

[ appended ]

the same is true for all logical disks i have: (c:\), (d:\) & (e:\).
there were no tasks in the background, no anti-virus/firewall/backup/rollback or mirroring utility running.
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ICE Graphics
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Joined: 31 Mar 2003
Posts: 430

PostPosted: Mon Dec 18, 2006 3:43 pm    Post subject: Re: although ICE ECC reports "Recover is possible" Reply with quote

It's a bug. New version v2.3 released
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gumbert-gumbert



Joined: 15 Dec 2006
Posts: 4

PostPosted: Tue Dec 19, 2006 6:30 pm    Post subject: Re: although ICE ECC reports "Recover is possible" Reply with quote


thank You! You've fixed it.
ICE ECC 2.3 shows no "Block write error" in the above-mentioned test.

but the "File read error" before the last 'damaged' block still persists.
it seems, it doesn't spoil anything though.

i've never seen it when file size is increased (or left unchanged).
it appears only when data file size is decreased!

hope, You'll find out what's it for.


but now, please, check this out:

1. i've pasted 1 byte at offset 512 in explorer.rar // blocks 2 - 717 are shifted
2. then, at offset 4608 (that is 9th virtual block's the very last byte) i removed 1 byte

// blocks 2 - 9 are shifted. but only 9th block is damaged
// that is we have 8 'damaged' blocks and only 7 recovery blocks

ICE ECC 2.3 reports:

Physical Memory - 511 MB
Memory Usage - 306 MB

Speed - 367.17 MB/Sec
Configuration - 1, 0, 4

Verify started: C:\temp;
Check - explorer.ecc
Use ECC file - C:\temp\explorer.ecc
Verify Data Files
Damaged block - 2
Damaged block - 3
Damaged block - 4
Damaged block - 5
Damaged block - 6
Damaged block - 7
Damaged block - 8
Damaged block - 9
Verify ECC Files
Search - explorer.rar
Found block - 2
Found block - 3
Found block - 4
Found block - 5
Found block - 6
Found block - 7
Found block - 8
Some files are damaged. Recover is possible
Copy files
Matrix calculation - 0
Recovery Data Files
Block read error - 10, B // here's where "Block read error" comes out!
Recover failed
Verify failed

Sad


if Log is to be trusted, nothing is recovered.
explorer.rar has been changed though (since md5 hash differs).
ICE ECC 2.3 has repaired it somehow ... partially !

out of curiosity i've started verification process one more time:
(remark: i mean i've closed the app. and started it again)

ICE ECC 2.3 reports:

Physical Memory - 511 MB
Memory Usage - 306 MB

Speed - 373.63 MB/Sec
Configuration - 1, 0, 4

Verify started: C:\temp;
Check - explorer.ecc
Use ECC file - C:\temp\explorer.ecc
Verify Data Files
Damaged block - 9
Verify ECC Files
Some files are damaged. Recover is possible
Matrix calculation - 0
Recovery Data Files
Finalization
All files succesfully recovered
Verify finished

Smile


so ICE ECC 2.3 has recovered explorer.rar IN 2 PASSES !!!

is it Bug?!
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ICE Graphics
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Joined: 31 Mar 2003
Posts: 430

PostPosted: Tue Dec 19, 2006 8:00 pm    Post subject: Re: although ICE ECC reports "Recover is possible" Reply with quote

gumbert-gumbert wrote:
if Log is to be trusted, nothing is recovered.
explorer.rar has been changed though (since md5 hash differs).
ICE ECC 2.3 has repaired it somehow ... partially !

I can not reproduce this is problem. Everything is work fine. Can you send damaged explorer.rar + ecc file to support@ice-graphics.com ?
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gumbert-gumbert



Joined: 15 Dec 2006
Posts: 4

PostPosted: Wed Dec 20, 2006 7:20 pm    Post subject: Re: although ICE ECC reports "Recover is possible" Reply with quote


i've already sent them.

b2f2b17fabc1a5e7aa37fa6661481f91 *explorer.rar
d3bb5e49a9a8721ef48acc43bd906bf2 *explorer.ecc

just paste 1 byte at offset 512 and remove 1 byte at offset 4608.

but, You know, it doesn't matter what sample data file to use.
i used .rar archive only as a reference to estimate ICE ECC's potential.
i've reproduced the same result with other files of the same & different size, filled with random bytes. and i've repeated all modifications i did before, but "Block read error - X, B" is still there.

here X stands for ("number of the first shifted virtual block" + "total number of recovery blocks" + 1)

for a sample file noname.dat of exactly 1MB in size, filled with random bytes,
i've created noname.ecc file with block size = 512 bytes, and total number of recovery blocks = 20.

so, if i paste 1 byte at offset 512 (decimal) and then remove the last byte of block 22 (at offset: 11264) - i have the same "Block read error - 23, B"
(23 = 2 + 20 + 1)

ICE ECC 2.3 log. pass one:

Physical Memory - 511 MB
Memory Usage - 306 MB

Speed - 364.75 MB/Sec
Configuration - 1, 11, 9

Verify started: C:\temp;
Check - noname.ecc
Use ECC file - C:\temp\noname.ecc
Verify Data Files
Damaged block - 2
Damaged block - 3
Damaged block - 4
...
Damaged block - 20
Damaged block - 21
Damaged block - 22
Verify ECC Files
Search - noname.dat
Found block - 2
Found block - 3
Found block - 4
...
Found block - 19
Found block - 20
Found block - 21
Some files are damaged. Recover is possible
Copy files
Matrix calculation - 0
Recovery Data Files
Block read error - 23, B
Recover failed
Verify failed

i exit ICE ECC 2.3, start it again and press "Verify" button one more time
// i emphasize, one should close the app.
// if you don't - you see nothing but errors)

ICE ECC 2.3 log. pass two:
Physical Memory - 511 MB
Memory Usage - 306 MB

Speed - 363.88 MB/Sec
Configuration - 1, 0, 4

Verify started: C:\temp;
Check - noname.ecc
Use ECC file - C:\temp\noname.ecc
Verify Data Files
Damaged block - 22
Verify ECC Files
Some files are damaged. Recover is possible
Matrix calculation - 0
Recovery Data Files
Finalization
All files succesfully recovered
Verify finished

recovered ! in 2 passes.
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