Hi! A dm-era device created over a RAID5 array loses discard support. Test script is attached. If you run it on SSD you'll see something like: loop0 4096 loop1 4096 loop2 4096 loop3 4096 md55 1048576 loop_test_era 0 I.e. mdadm device supports discard, but dm-era device started over it doesn't. If you create a dm-era device over a normal block device without mdadm RAID5 or even over mdadm RAID1 - it will preserve discard support. Why? How can it be fixed? -- With best regards, Vitaliy Filippov
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raid5_test.sh
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