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An excerpt from dmesg:

md: Autodetecting RAID arrays.
md: Scanned 2 and added 2 devices.
md: autorun ...
md: considering sdb1 ...
md:  adding sdb1 ...
md:  adding sda1 ...
md: created md1
md: bind<sda1>
md: bind<sdb1>
md: running: <sdb1><sda1>
raid1: raid set md1 active with 2 out of 2 mirrors
md1: detected capacity change from 0 to 1500299198464
md: ... autorun DONE.
 md1: unknown partition table
EXT3-fs (md1): error: couldn't mount because of unsupported optional features (240)
EXT2-fs (md1): error: couldn't mount because of unsupported optional features (240)
EXT4-fs (md1): mounted filesystem with ordered data mode

Is it OK that kernel tries to mount an ext4 raid as ext3, ext2 first?
Is there a way to tell it to skip those two steps?

# mdadm --detail --scan
ARRAY /dev/md/1 metadata=0.90 UUID=56851215:5dca6eee:776c2c25:004bd7b2

# grep dev/md /etc/fstab
/dev/md1                /               ext4            noatime         0 1


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Yes, it's perfectly normal that the kernel probes the filesystem for the correct driver to use to mount the file system. I've had a Linux box before probe for XFS, JFS, and a few others before it got to loading the ext4 driver up. The only harm was the error messages in dmesg.

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it has nothing to do with RAID. the only interesting snippet is the one of /etc/fstab; but for / you have to check the /etc/fstab included in the initramfs file.

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Thanks. Initramfs is a generic one produced by genkernel: /dev/ram0 / ext2 defaults 0 0 – yanchenko Mar 21 '10 at 20:33

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