Previous 1 2 3 4 Next 117 Replies Latest reply: Feb 28, 2015 11:53 AM by R.K.Orion Go to original post
  • Grant Bennet-Alder Level 9 Level 9 (51,750 points)

    A Hard Drive drive spinning at 7200 RPM turns the platters 120 times a second. That does not produce a signal with 5.5 seconds periodicity.

  • MrJavaDeveloper Level 1 Level 1 (60 points)

    An irregularity means it took Scannerz xxx.xx seconds to read a sector or group of sectors. Considering the overhead associated with the operation coming from the drive controller, the OS, and Scannerz itself I don't know if you can or could correlate such a thing directly to RPM. Besides that, he was talking about an old aluminum PowerBool that would have likely had a 5400 RPM drive in it anyways.

  • Grant Bennet-Alder Level 9 Level 9 (51,750 points)

    If it took 5.5 seconds to read a block, that is clearly caused by Bad [or marginal] Blocks. The data are written with an error-correcting code that can handle a few bits flipping, and the drive, Driver, and Mac OS X will each re-read in an attempt to get correctable data. 5.5 seconds could easily elapse waiting for correctable data. If it gets correctable data, it is read as good and you move on. If it never does, you do the maximum number of re-tries and then I/O Error is declared. Sometimes everything comes to a Halt.

     

    The conventional method for working around Bad Blocks is to provide good data to re-write the marginal Block. In bulk, this is accomplished by Zeroing the drive (the option is available under Disk Utility Security Erase). If too many [typically 10] blocks are replaced by the drive's spares, you will get "Initialization Failed!". Whether you choose to run it again to see if the drive will come clean is a complete judgement call.

     

    Google did studies on very large numbers of consumer-class drives used in their "always on" Server farms. Their data indicate a drive that develops Bad Blocks -- in their type of use -- will end up developing so many additional Bad Blocks it will be replaced with six months.

  • MrJavaDeveloper Level 1 Level 1 (60 points)

    I'm not sure what you're arguing about. Your original comment made it sound like 5.5 seconds was impossible, yet your answer above in the very first paragraph above explains why he could get a 5.5 second reading.

  • Grant Bennet-Alder Level 9 Level 9 (51,750 points)

    Sorry, I don't mean to sound mean.

     

    The first time someone said 5.5 seconds, It sounded like an error was occurring with a frequency of every 5.5 seconds, and this was blithely written off to Bad Blocks.

     

    But once you explained what that message really meant, I agreed with you, and wanted to add some insight about what was happening to have it take that long.

     

    Then I wanted to add some info for the Original Poster about some practical ways to address such a problem.

     

    Sometimes this is boring stuff that "everybody" has heard before. But occasionally, Readers have never heard about some reasons for doing things a certain way.

  • ThomasB2010 Level 1 Level 1 (5 points)

    I don't see any reason for you to apologize for your comment. I see how you made the mistake. He said "this is repeatable." You're just not familiar with the tool.

     

    With Scannerz if you find a problem you re-evaluate it in cursory mode to confirm the problem can be repeated. For example, if a bad block is found at sector 543,343,104, and you rescan over it in cursory mode, the same block shows up as bad every time you rescan it. WIth cursory mode you can evaluate a small section of the drive without needing to re-test the whole drive.

     

    If it's repeatable you're just about certain it's a problem with the drive surface. If it can't be repeated, or worse yet, crops up in other places, most of the time it's a cable with an intermittent fault, or it could be a problem with the system. That's why I think so many people are beginning to like this tool. To the best of my knowledge other tools wouldn't even pay attention to a timing irregularities, regardless of whether or not it's drive or cable related, and they identify all I/O errors during a surface scan test as sector/block errors, even if they're being caused by a bad cable.. If an I/O error is being caused by a cable problem, you can replace your drive as many times as you like, and I guarantee you, the problem will still be present.

     

    Based on some of the comments I've seen on this site, apparently SATA cables can be problematic on some of these units.

  • R.K.Orion Level 1 Level 1 (5 points)

    Thanks for all the input guys. The MacBook's that I was testing today are holding up a bit better than the PowerBooks did. Only a few had optical drive problems and only one had a bad drive (genuinely bad sectors this time) It's too bad the MacBook Pro's that I'll be looking at next can't have the HDs swapped out as easily as it can be done on the MacBooks. That was a real asset - a 5 minute job, and that's when I'm taking my time.

  • ZV137 Level 1 Level 1 (45 points)

    One of the things you need to be aware of is what I call the "SATA cable conspiracy." A few people have detected problems with their SATA cables and have menaged via the web to translate this into an "epidemic." As far as I'm concerned there's no real evidence of an "epidemic" of these failing. Most likely mentioned are MacBook Pros from 2006 -2010.

     

    Since you're starting on the MacBook Pro's I just thought I'd throw that out for you so you don't pre-judge a potential problem.

  • Grant Bennet-Alder Level 9 Level 9 (51,750 points)

    ZV137-

     

    You bring up a good point. We would expect that these cables, consisting of only wires, would essentially never fail in normal use.

     

    But they are implemented as flex cables because these Macs are portable, and can occasionally be subject to stress and vibration. The hard drive is one of the heaviest things mounted on a flex cable.

     

    Based on user anecdote, these cables do occasionally fail. But my impression is that the failure rate for these cables is still exceptionally low. The surprise is that it is not quite zero (but close).

  • R.K.Orion Level 1 Level 1 (5 points)

    We're doing the MacBook Pro's now. It's quite surprising to me how well these units are holding up after all these years. We've hardling encountered any problems at all. So far we've found about 5 HDs with problems out of all the Intel lots. We do have one 2006 MacBook Pro that's exhibiting fairly bizarre behaviour and I suspect the RAM may be loose or bad on it. That will need more looking into.

     

    I showed this link to the boss and he pretty much concluded that the PPCs are probably best being donated, or we can give them to employees. Maybe their kids can use them for something. I thought about taking some home myself, but I have this vision of my wife grabbing one of the PowerBooks and hitting me over the head with it while shouting "More computers!?!?!? More computers!?!?!?"

  • ZV137 Level 1 Level 1 (45 points)

    R.K.Orion wrote:

     

     

    ......I thought about taking some home myself, but I have this vision of my wife grabbing one of the PowerBooks and hitting me over the head with it while shouting "More computers!?!?!? More computers!?!?!?"

     

    Know the feeling all too well, my friend!

     

    There seems to be a discrepancy in some of the posts about optical drive longevity. Some are saying they're unreliable, another is saying they're very reliable. What's your opinion?

  • R.K.Orion Level 1 Level 1 (5 points)

    Personally, I think it would be difficult to really assess just exactly how well optical drives hold up to use. Unlike hard drives that are being used by the system all the time, optical's are used on demand. Back in the old days I could see people using the optical drives to play CDROMs or DVDROMs for music and video because the drive space was limited. For example a lot of the PowerBooks we have only have 40GB, 60GB, or 80GB drives, which isn't much by todays standards. People might be inclined to use them more back in those days because if you had a lot of songs putting them on an HD would eat up a considerable amount of drive space. With the advent of larger affordable drives, I would suspect more and more people would start putting their music onto the hard drives and not using the optical drives at all. It's tough to tell.

     

    The only thing I use optical media for anymore is if we have an old (pre-Lion) system and need to load the install disks, usually because we need to access Disk Utility or a user screwed up passwords or better yet, forgot them. I download all my music from the iTunes store, and I've long since loaded all my music onto my systems years ago. I can't even remember the last time I actually put a CDROM into a system to play music.

     

    One 2006 MBP is exhibiting what the Scannerz manual calls "unrepeatable, inconsistent irregularites" or something like that. I actually can get some irregularities running almost 15 seconds. Never repeatable. According to their documentation the most likely cause might be a cable problem or a problem with the logic board. I guess we'll have to take a better look at that one, but so far that's the only one we've seen with anything approaching a significant problem, meaning a possible actual system problem. I'll use their little path isolation tactic using an external drive to see if I can isolate the problem.

     

    I'm pleasantly surprised at the quality of Scannerz. I never heard of it before and was really afraid it was going to be a fly-by-night piece of junk but thought I'd try it because it didn't cost much. It's actually quite good and quite thorough. I'm anxious to play with FSE too, but haven't had that much time.

  • PlotinusVeritas Level 6 Level 6 (14,705 points)

    What's wrong with "more computers" ?    I've got 50 some dead laptop computers downstairs.

     

     

    Give them to the kids to tear apart.   Very very educational, fun, builds skills.

     

     

    All children should get a pile of dead computers to take apart and examine.

     

    better than a stinky frog in a science lab.

  • ZV137 Level 1 Level 1 (45 points)

    Obviously yoiu don't have an "overlord" for a wife!

  • CaptH Level 1 Level 1 (50 points)

    R.K.Orion wrote:

     

    We're doing the MacBook Pro's now. It's quite surprising to me how well these units are holding up after all these years. We've hardling encountered any problems at all. So far we've found about 5 HDs with problems out of all the Intel lots. We do have one 2006 MacBook Pro that's exhibiting fairly bizarre behaviour and I suspect the RAM may be loose or bad on it. That will need more looking into.

     

    I assume that you're talking about working units only and that you've at least had some units with problems that didn't get tested, right? Surely you had some other units that failed for one reason or another that didn't get tested, right? I'm not implying Apple has bad hardware, they have some of the best, but it would be odd to see 100% of a set of computers have only minor problems.

     

    Regarding the unit you have with erratic problems, it's likely the cable but before opening the unit up I'd check the RAM and it's seating because it's easy to do and a good possibility. Scannerz **will** pick that stuff up too, but you have to go through the system to isolate it. I'd advise just checking that first because it's easy.

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