Re: [gentoo-user] Testing a used hard drive to make SURE it is good.

[madscientistatlarge <madscientistatlarge@protonmail.com>]

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I just tested a couple of 4TB drives, the hgst 7k400 series (7200 rpm), it takes about a day to fill one of those, copying from another one of those. I prefer to use "real" data, rather than a test pattern. My procedure is to first run the short SMART test, format the drive (which also takes awhile..) and fill it with data. I like to copy to the test drive from 2 drives at the same time, producing fragmentation, and then copy what's on the test drive already into a new folder on the test drive and repeat, it makes it a brutal mechanical test. After that I fsck it, power cycle the computer/drive, run fsck again, and then run the drives long SMART test, which does take a looong time, and then run badblocks which should find nothing. I've had a drive that tested fine but would corrupt data (I don't know if the drive electronics started doing random writes or what, this wasn't an '80's drive), often within minutes, which is part of why I power cycle, and why I use fsck after putting data on the drive. I of course I then reformat the drive. It does bloody take days, plan to not be watching it. I've done this on my main machine as it doesn't hurt anything else. These are Refurbished drives in this case, going into a raid 6 to try and end bitrot, which I"ve seen too much of using similiar drives, it tends to slowly delete scenes from video when this happens without any indication (other than not showing things you know are in the video from watching before).

It's a major pain, but so is watching stuff get corrupted! Note that a failing power supply can make a drive look like it's failed, seen this a couple of months ago. As soon as I put the drive in question on an external supply it magically worked fine. Did this right after another drive appeared to fail the same way (different brand). Apparently one drive was more sensitive to bad power then the other, both drives are in fact fine! I've also seen ram repeatedly test bad with a failing power supply. Not really surprising that a failing power supply can make things look bad. What was unexpected was the subtlety of the failure over time. Lesson being to always test drives that just failed on another machine, or with external supply and usb adapter after the machine boots to an OS (also great drives that have failed so that they delay/block even the BIOS from coming up, which failing drives can do). Obviously checking the power supply is always a good idea, though substituting another supply works. Power supply failures are not always apparent with a voltmeter as they can be noisy and your' meter won't tell you that generally. Also of course, ALL of this can be temperature sensitive and hence intermittent, I've done repair work, intermittent failures can take you all over trying to find them, random correlation abounds and misleads! So if the drive does appear to fail, it may or may not be the drive. I mention this as it's really annoying to find the real issue after replacing parts that weren't bad and possibly throwing out perfectly good hardware.

I did get a refurbished drive that was invisible to the bios, and wouldn't work externally on a different supply either. Can't be sure until you try it on a different machine or external.

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‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Monday, June 15, 2020 10:07 AM, Dale <rdalek1967@gmail.com> wrote:

> Howdy,
>
> I finally bought a 8TB drive. It is used but they claim only a short duration. Still, I want to test it to be sure it is in grade A shape before putting a lot of data on it and depending on it. I am familiar with some tools already. I know about SMART but it is not always 100%. It seems to catch most problems but not all. I'm familiar with dd and writing all zeores or random to it to see if it can in fact write to all the parts of the drive but it is slow. It can take a long time to write and fill up a 8TB drive. Days maybe?? I googled and found a new tool but not sure how accurate it is since I've never used it before. The command is badblocks. It is installed on my system so I'm just curious as to what it will catch that others won't. Is it fast or slow like dd?
>
> I plan to run the SMART test anyway. It'll take several hours but I'd like to run some other test to catch errors that SMART may miss. If there is such a tool that does that. If you bought a used drive, what would you run other than the long version of SMART and its test? Would you spend the time to dd the whole drive? Would badblocks be a better tool? Is there another better tool for this?
>
> While I'm at it, when running dd, I have zero and random in /dev. Where does a person obtain a one? In other words, I can write all zeros, I can write all random but I can't write all ones since it isn't in /dev. Does that even exist? Can I create it myself somehow? Can I download it or install it somehow? I been curious about that for a good long while now. I just never remember to ask.
>
> When I add this 8TB drive to /home, I'll have 14TBs of space. If I leave the 3TB drive in instead of swapping it out, I could have about 17TBs of space. O_O
>
> Thanks to all.
>
> Dale
>
> :-) :-)

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