@wurtel: You mean read and write are disabled? I cannot find any complete documentation on the output of gpart geom so I do not know how to interpret the Mode field.

@dirkt: However, it works without any problems under Linux. In any case, should I repartition the disk? Is it possible to change the sector size using a partitioning tool?

What puzzles me is that both disks are the same model, bought at a few months distance. Why do they have different physical block sizes?

@dirkt: If this were the case, the problem should disappear when I remove the good drive (?) Anyway, running gpart list with only the bad drive attached gives the same result for stripesize and stripeoffset.

I had a similar problem (i.e. block size mismatch) once which had the origin of using the disk in an external enclosure: Some of these (e.g. USB3 HDD case) will map the drive from/to 512/4096 block size. I solved the problem by taking the risk (!) of deleting and re-creating the partition table by searching for the start sectors using the other unit (don't remember which way around it was). The FS and data was still there and intact. Could this be the source of the problem?

I bought the disks with a built-in enclosure and I plug them directly on my computer using a USB cable. So there is nothing but the USB cable between the disks and my computer. Repartitioning the disks is not a problem: I am backing up my data right now, should be finished in one hour or so. I want to try using 512 logical sectors since, as far as I understand, it is not possible to change the physical sector size, because that is determined by the controller.

@Giorgio "There is nothing but the USB cable..": This is not really true. The disk is most probably a SATA disk, and there is an electronics board with firmware which bridges/translates between USB and SATA. This is where the changeover of logical unit size can take place (and it did in my case). Once removed from the enclosure I needed to fix the partition table accordingly, which carries a risk. -- Are the 2 disks (+enclosures) identical? Has any one of them been taken out of the enclosure? Is it possible it "changed" the allocation size at that moment?

@Ned64: The enclosures are identical and both disks are sold by the same company as 1T external drives. However, I found out that internally two different disks are used, even the vendors are different. I made further experiments and have posted a question on the FreeBSD forum (forums.freebsd.org/threads/58489).

@Ned64: More precisely: Does FreeBSD have problems using ext2fs with external USB hard drives that have a sector size of 4096 Bytes? I tested ufs on this drive and it seems to work OK.

Yes, indeed. Sadly, I do not know it :-( It is, however, good, to have a precise question (for the FreeBSD developers, I suppose?!).

FreeBSD itself can apparently handle the blocksize: bxr.su/s?refs=e2fs_bsize&project=FreeBSD and svnweb.freebsd.org/base/head/sys/fs/ext2fs/…

@Ned64: Thanks for all the feedback. I have considered compiling the package from source and possibly inserting a few printfs to debug it.

This could also help (unless this is you): daemonforums.org/showthread.php?t=9572

Hello, thanks for the link. It is not me

There is no open bug on FreeBSD that has ext2 or ext2fs in its name.

I have changed the title of the question on stackoverflow and on the FreeBSD forum. Maybe a developer will take a look at it? Otherwise I can file a bug.

Are you using FreeBSD? I have just started.

I would file a bug right away. You have spent quite some time already.

No, I am not using FreeBSD (yet), only GNU/Linux.

I have also used mainly GNU/Linux up to now. I am seriously considering FreeBSD.

I am planning to have a look at it, too, when I have the time. It looks like a pain, though, since I have all my data on ext4 FS.

I also had this problem. I copied the data to my main hard disk, reformatted with ext2, and copied it back. Before that I had installed it on a spare hard disk. You can find a second hand sata hard disk for very little money.

Anyway, I am filing a bug report right now.

Here's the bug: bugs.freebsd.org/bugzilla/show_bug.cgi?id=214479

I am not copying 30 TB of data from ext4 to ext2/XFS! :-)

How many disks do you have?

10

not counting SSDs

So, I'lll stick with an ext4-friendly OS for the moment....

I have first tried FreeBSD on an old computer for a while. Now I have decided to use it on my main PC. I do not have that much data: about 400 G in total.

Which GNU/Linux distribution are you using?

Several, from CentOS to Arch.

I am going to have some dinner now. Thanks for the info and the chat. Maybe we catch up with each other some other time.

Great :-) Keep me posted about the problem!