RAID1: Which disk will be mirrored?

Posted by tmelen on Server Fault See other posts from Server Fault or by tmelen
Published on 2012-10-07T19:57:47Z Indexed on 2012/10/07 21:40 UTC
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raid

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mdadm

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raid1

How does a RAID1 system determine which disk to use as the source and which disk to use as the destination when mirroring?

Assume for instance the following scenario: A RAID1 array is created with two disks A and B. A is replaced by disk C, which is added to the array. Files are beeing modified as time goes by. Now B is removed and A is reinserted.

Will the RAID1 system realize that A and C are out of sync? And that C is more up-to-date than A? And if not, is there a safe way to avoid the mirroring process to start immediately when disk A is inserted?

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