Is that normal a removed part in RAID0 still showed as "active sync"

The /dev/md0 is set as RAID0
"cat /proc/mdstat" shows
md0 : active raid0 sda1[0] sdd1[3] sdc1[2] sdb1[1] 157307904 blocks 64k chunks

Then sdd is removed.

But "cat /proc/mdsta" still shows the same information as above, while two RAID5 devices show their sdd parts as (F)
md0 : active raid0 sda1[0] sdd1[3] sdc1[2] sdb1[1]
157307904 blocks 64k chunks

Is this normal?

Also, when using "mdadm --detail"
sdd1( part of RAID0) is showed as "active sync", but sdd2(which is part of RAID5) is showed as "removed"

Thank you.

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Yes.

raid0 is not real raid. It is not able to cope with disk failures, so it doesn't even try. Devices in a raid0 are never marked failed as doing so would be of no benefit.

NeilBrown

Thanks. That's really helpful.

When doing this, I used "tail -f /var/log/messages" to monitor my program, which does I/O to md0.

After sdd was removed physically, it seemed the I/O operations to the md0 continued:
"tail -f /var/log/messages" occasionally shows:
SCSI error: return code = 0x00040000
kernel: end_request: I/O error, dev sdd, sector 15357599
but showed all the other messages just as sdd was still there.

Is this normal?

I am really not sure whether the result of my program is still trustable.

Also, if sdd1 is the only device which fails, is there any way to know it? Just as what "mdadm --monitor" does?

Thank you.