Raid 1 with mdadm, restarting causes full reconstruction
 

Hi all, I'm using mdadm to to a level 1 raid on two disks (obviously). When I take out disk A and immediately put it back in, it resyncs without a problem without a reconstruction. But if I restart with drive B at the helm, then put A back in after the restart, it does a full reconstruction on A even though nothing has changed. Any idea why this is? (My bitmap is set to internal). I know mdadm is complicated and I should be providing a lot more information, but any vague ideas?

It probably looks at the reboot - possibly a journal has changed - and decides it needs to rebuild. You can add the drive back in and tell mdadm not to resync, but that can be risky.

Are you doing this on a regular basis or just testing it out?

Just testing.