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#21
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check or scan _without_ retesting sectors?
"J. P. Gilliver (John)" wrote in
: How many retries is too many though? I _think_ SpinRite (or whatever it was) had a settable maximum, though that could be disabled. Even one. Can be, anyway. Hence read-only, as lightly as possible, writing to images. Maybe once that's done, if the source survived, some attempt at averaging might warrant a few re-reads, but I wouldn't to it. Better to wait, use DRY cooling, no humidity, to cool the source by at least 10°C, then try one clean pass to a second image, then more cooling, a third image, etc, then average the clones wherever they differ. Tedious, no wonder data recovery can cost so much.. |
#22
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check or scan _without_ retesting sectors?
"J. P. Gilliver (John)" wrote in
: I notices that in protected mode good data seems to copy MUCH faster than in DOS. I still don't know enough to know exactly why, but I suspect that if anything causes slow reading of data, you might as well do it in DOS so you have safe direct hardware access. I can't remember what protected mode means, but I vaguely do remember some copying going faster - I think it was floppy to floppy on the same drive (remember "insert source disc"/"insert destination disc"?), where I assumed it had a much bigger buffer in the more advanced mode. Protected more is 32 bits, basically a virtual machine. Which may just mean that some stores are in RAM, managed by code also in RAM, which speeds things up. I think DOS could speed handling of floppies by RAM caches too, letting the user set sizes that may or may not restrict other uses of RAM. Not related, but general good advice: Franc Zabkar mentioned the hazards of tools that repeatedly hammer a disk, especially when data is already hard to read off it. What is not often noticed by people is that the disk may be hard to read becaus it has already been hammered to hell in 'normal' use. When I make large backups I always use a different disk, not just a different partition. Personally, I find it SCARY, that horrible juddering noise when copying gigabytes around between partitions on the same drive. No matter how quiet it is in modern drives, I try to avoid it. I prefer to leave that kind of motion to galvanometer laser scanners where there's no choice in the matter. |
#23
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check or scan _without_ retesting sectors?
On Sat, 19 Nov 2011 23:18:22 +0000, "J. P. Gilliver (John)"
put finger to keyboard and composed: In message , Franc Zabkar writes: On Sat, 19 Nov 2011 08:56:28 +0000, "J. P. Gilliver (John)" put finger to keyboard and composed: I saw [SpinRite] being used on the drive from a DOS ('286-based, IIRR) machine. I'm pretty sure it was a lot less than 200M. That's where I first encountered SpinRite. It was great on those old stepper motor drives. A much better approach to data recovery is to clone the drive, sector by sector, using a utility that understands how to work around bad media. Two examples are ddrescue and dd_rescue, both freeware. How do they handle bad sectors though? Just give them a default value? Zeros, I think. Personally I'd like to see bad sectors filled with a repeating "BAD" text string, or some other value that the user could define. A good standalone DOS utility that can perform a surface scan on your drive is MHDD. It will identify "slow" blocks, ie those that require several read retries. How many retries is too many though? I _think_ SpinRite (or whatever it was) had a settable maximum, though that could be disabled. The drive automatically retries difficult sectors, without software intervention. ISTR that a typical maximum number of retries could be around 10 or so. Some drives support Error Recovery Control (ERC) which sets the timeout values for reads and writes. That is, if a drive is unable to complete a read or write request within the ERC limits, then it aborts the command and returns a failed status. Samsung calls this feature CCTL (Command Completion Time Limit), while WD refers to it as TLER (Time Limited Error Recovery). ISTR that some enterprise drives (eg SCSI or SAS) allow the maximum number of retries to be set by software via a specific mode page. - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#24
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check or scan _without_ retesting sectors?
Franc Zabkar wrote in
: Personally I'd like to see bad sectors filled with a repeating "BAD" text string, or some other value that the user could define. 42 41 44 21 00 BB AA DD BAD!.»ªÝ ? Best I could do for a clean fit to 512 bytes. Or just 4 for text only, BAD!... Using the map of bad sectors from the log file, this could be done. |
#25
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check or scan _without_ retesting sectors?
In message ,
Lostgallifreyan writes: [] I also saw a forceful recommendation for this: http://www.datarescue.com/photorescue/v3/drdd.htm ...but I have no situation that can let me judge how good it is when it really matters. Strange, the link in your post was to "http://www.datarescue.com/photorescue/v3/drdd.htm...but". (Obviously I figured it out.) Looks useful; always good that it's free, but even so, good. The log files seem a good idea. Since it seems to be designed among other things for memory cards as well as hard drives, I can't see why it wouldn't work with floppies too. -- J. P. Gilliver. UMRA: 1960/1985 MB++G.5AL-IS-P--Ch++(p)Ar@T0H+Sh0!:`)DNAf "Bother," said Pooh, as Windows crashed for the umpteenth time. |
#26
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check or scan _without_ retesting sectors?
"J. P. Gilliver (John)" wrote in
: Strange, the link in your post was to "http://www.datarescue.com/photorescue/v3/drdd.htm...but". (Obviously I figured it out.) I guess some clients don't treat a newline as space. Looks useful; always good that it's free, but even so, good. The log files seem a good idea. Since it seems to be designed among other things for memory cards as well as hard drives, I can't see why it wouldn't work with floppies too. Exactly. I snagged a copy because memory cards are something it really might impress me on some time. I sometimes have trouble with those and haven't really thought beyond using another, and a backup placed on it. I use an SD card for GPS logging, and might lose data that DRDD can save. Being able to resume a long trawl like ddrescue can do seemes to be another specialty of DRDD which may be directly inspired by the GNU program for all I know... |
#27
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check or scan _without_ retesting sectors?
Lostgallifreyan wrote in
: it really might impress me on some time Or possibly not. Ò^O I have three hard disks and a RAM drive in my system and it can't see any of them. |
#28
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check or scan _without_ retesting sectors?
Lostgallifreyan wrote:
"J. P. Gilliver (John)" wrote in : Strange, the link in your post was to "http://www.datarescue.com/photorescue/v3/drdd.htm...but". (Obviously I figured it out.) I guess some clients don't treat a newline as space. Well, they're not the same! A new line is 0AH (hex), and a space is 20H. Viva la difference! :-) |
#29
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check or scan _without_ retesting sectors?
"Bill in Co" wrote in
m: Lostgallifreyan wrote: "J. P. Gilliver (John)" wrote in : Strange, the link in your post was to "http://www.datarescue.com/photorescue/v3/drdd.htm...but". (Obviously I figured it out.) I guess some clients don't treat a newline as space. Well, they're not the same! A new line is 0AH (hex), and a space is 20H. Viva la difference! :-) Well, in this case it ought to be, then the URL would not have been run into the test starting the folowing line. If you look at most if not all RegExp (regular expression syntax), you'll see a few other related hex codes, 09 for tab, and A0 (dec 160), looks like a space but isn't, which can be profoundly useful or extremely annoying depending on context. Then there's 0D as well as 0A, hopefully in that order, and ALWATS together in emails, stuff breaks otherwise. And so it goes. And because of the rules being complex, RegExp calls the whole lot of it 'whitespace'. You can be very specific about each type with RegExp too, but sometimes the similarity is all that matters, especially if all that space is a an undesired thing to ignore. Pus ca change, pus ces't la meme chose! Not very Francais, exactly, nes't pas? Do you know, I had that slightly sickening pun in a forum sig for several years... |
#30
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check or scan _without_ retesting sectors?
Lostgallifreyan wrote:
"Bill in Co" wrote in m: Lostgallifreyan wrote: "J. P. Gilliver (John)" wrote in : Strange, the link in your post was to "http://www.datarescue.com/photorescue/v3/drdd.htm...but". (Obviously I figured it out.) I guess some clients don't treat a newline as space. Well, they're not the same! A new line is 0AH (hex), and a space is 20H. Viva la difference! :-) Well, in this case it ought to be, then the URL would not have been run into the test starting the folowing line. If you look at most if not all RegExp (regular expression syntax), you'll see a few other related hex codes, 09 for tab, and A0 (dec 160), looks like a space but isn't, which can be profoundly useful or extremely annoying depending on context. Then there's 0D as well as 0A, hopefully in that order, Indeed. First the CR, then the LF. Not sure how things would work out if it were reversed, though. On further thought, I don't think too well; the cursor or print head might actually drop down an additional line, then (not sure, though). and ALWATS together in emails, stuff breaks otherwise. And so it goes. And because of the rules being complex, RegExp calls the whole lot of it 'whitespace'. You can be very specific about each type with RegExp too, but sometimes the similarity is all that matters, especially if all that space is a an undesired thing to ignore. Pus ca change, pus ces't la meme chose! Not very Francais, exactly, nes't pas? Do you know, I had that slightly sickening pun in a forum sig for several years... Pus or Plus? I'm assuming that was to mean "the more things change, the more things remain the same". Ain't it the truth. :-) |
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