Re: Schrödinger's hash

On Fri, 22 May 2026 09:53:17 -0600 Charles Curley wrote:
 > I have four four terabyte hard drives. Each has a partition on it. The
 > four partitions comprise a RAID 5 array using mdadm. On top of that,
 > LUKS encryption, then LVM with ext4 logical volumes.
 >
 > On one LVM partition I have a number of backup files, tarred,
 > bzipped, and sha256 and sha512 summed. I have a script which will find
 > checksum files, and execute the appropriate program to test the
 > archives. It puts each program into the background, parallising any
 > number of checksum tests.


On 6/21/26 14:05, Charles Curley wrote:
> I believe I have found a solution to this problem. I installed the
> backports kernel. Since then I have run more than four hours solid of
> tests and not found a single error.
> 
> I did replace one hard drive. While that resulted in a quieter office,
> it did not solve the problem.
>
> Checking voltages from the power supply and the wall with a digital
> volt meter did not show any out of spec problems.


I am glad that your storage is working correctly now.


Please run and post the following commands with both the previous kernel 
and the backports kernel:

$ cat /etc/debian_version

$ uname -a


I will assume your script spawns a separate, isolated process for each 
checksum file.


If you have ruled out the power supply, memory, and disks, another 
possibility could be a race condition in the kernel and/or I/O stack 
that is triggered when multiple processes access storage in parallel.


Are the checksum errors repeatable on another computer with a similar 
storage architecture and the previous kernel?  If so, do they disappear 
with the backports kernel?


David