Logical volume that spans raid1 sets: what happens if a RAID fails?

Posted by Jeff Shattock on Super User See other posts from Super User or by Jeff Shattock
Published on 2010-05-18T03:40:45Z Indexed on 2010/05/18 3:52 UTC
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Filed under:

mdadm

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lvm

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failure

Consider the following scenario:

/dev/md0 - 10GB RAID 1 volume built from /dev/sda and /dev/sdb
/dev/md1 - 10GB RAID 1 volume built from /dev/sdc and /dev/sdd
/dev/vg0 - volume group containing md0 and md1
/dev/vg0/lv0 - 15GB logical volume

The raid devices are created with mdadm; the logical volumes by LVM.

What happens to lv0 if md0 fails entirely? That is, if both sda and sdb disintegrate so that the md0 device can not start. Is the portion of the data that resided on md1 still accessible, or is the entire LV gone? Would the answer change if lv0 were created as a striped volume vs non-striped?

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