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From: | Kevin Hubbard |
Subject: | [Bug-ddrescue] ddrescue errors: maybe yes, maybe no |
Date: | Tue, 11 Feb 2014 22:10:58 +0000 |
Good day,
I have used PayPal to send "ANTONIO" $15 EUR = $20 USD. Confirmation Number 7WL22909N9065834D on 2014-02-11 17:00 EST I am a first time user of ddrescue 1.17 (DL from tinyapps.org) MacBook Pro (15-inch, Late 2008, 2.4 GHz, 8 GB) Snow Leopard 10.6.8 Failing HDD is Toshiba AF Model DT01ACA200 Perhaps you might advise ... I am in the midst of trying to recover this failing HDD - no emergency here since this HDD is one half of a RAID-1 array and the other HDD is in good health. So in effect, this is an exercise for me to use ddrescue and get experience recovering data. How do I know the HDD is failing ? - heard awful noise coming from the array - ran smartctl which indicated several errors - split the array and reran smartctl to find the HDD in error - used CarbonCopyCloner to do a file-level copy to another disk - one file was flagged as unreadable (not copied) - tried Finder Copy/Paste on this file - quit half way through - system log shows either "I/O error" or "data underrun" However, - used DriveGenius read-only scan --> successful/no syslog errors - used TechToolPro read-only scan --> successful/no syslog errors - used BadBlocks read-only scan --> successful/no syslog errors Note, I have not done any read-write scans. And, Since it is not obvious to me what sector(s) are failing, I tried ddrescue with logfile, and found 1) -n -b 4096 -c 128 --> fails with 3 errors 2) -n -b 512 -c 512 --> fails with 3 errors 3) -n -b 512 -c 128 --> no errors 4) -n -b 512 -c 8 --> no errors I reran these 4 tests and got the same results. Note, I always interrupted ddrescue after 30000MB copied since the 3 errors, if detected, end around 22575MB. Saves time. So, My objective is to identify the failing hardware sectors and then try to have Mac OS X reassign alternates. As I understand it, this can be done implicitly: 1) Secure Erase the entire partition or 2) Secure Erase just the failing file and hope there are no other failing sectors in the free space or 3) Delete the failing file then Secure Erase all free space or 4) Use BadBlocks in Write-Mode on just the failing sectors Questions: 1) What is the correct Sector (-b hardware block) size for Advanced Function (AF) HDD in the Mac OS X environment - 512 or 4096 ? I did notice that ddrescue only accepts -b as 512 or some multiple of 512. 2) Why does changing the -b and -c values affect whether or not ddrescue encounters errors ? 3) Why does each output log start with "About to copy 9223 PBytes from /dev/rdisk5s2 ..." when the partition/volume is 1.5 TB ? 4) What does the ? in progress size value in the log always some gigantic number, such as 0x7FFFFFE89F8FFFFF ? Does it have meaning ? Since 0x7FFFFFE89F8FFFFF = 9223371936452570000 then perhaps this accounts for the 9223 PBytes message ... Summary, I am in no rush to recover data - except for one file, I have copied everything to another volume. After I decide what to do with the failing HDD, I will rebuild the array. Right now, I need to better understand how to use ddrescue. I have all relevant documentation - as requested, I will send it. Thx ... Kevin |
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