I have a question on RAID error detect. hope somebody can help me to find it out. thanks.
take raid1 as an example, if one disk fail, raid 1 can detect the data on disk is compromised and then reconstruct it using a spare disk. this is straight forward.
but if one request comes to raid1 and raid1 sends requests to both disks, at this time, system reboots because power outage, system crashes, or any other reason. then after system reboots, how raid 1 detects which disk has consistent data? since before reboot, anything can happen, data may in disk1 but not in disk2, or in disk2 but not in disk1, or not in both disks, or already on both disks.
how raid1 or other raid code deal with this?
In short, it does not deal with it at all. RAID will deal with a disk failure, it has no guarantees about consistency on power failures, hard lockups or other catastrophic events.
A UPS is cheap insurance against consistency issues in combination with a journalling filesystem.
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