Can I write data safely to a RAID-1 ARRAY while it is resyncing?

Question

Will the files be in all drives on the array when the sync is complete?
What if a disk fails while sync is in progress?

Solution

• You can safely write to any degraded RAID array and not lose any data, that's a standard RAID feature
• If a disk fails during sync, well it matters which disk that failed. If it was the resync target, who cares, it'll just resync from the master again. If it was the master then the RAID 1 has failed however that member still has the most up to date copy of the data. So if it's a transient error your data is probably fine, the system reboots and resync attempts to continue, if it's not then you've exceeded the protections provided by RAID 1 and have now lost data
• No RAID is a substitute for regular backups aka duplicity or plain old rsync.

Comments

[K2Chris1983]

From my research, "One can directly start using it while mdadm resyncs the array in the background." Now is this software or hardware RAID, etc. If it's software RAID you can check the process by $ cat /proc/mdstat

[K2Chris1983]

I like bullet three =) You got my vote!

[rudolfbyker]

Do you mean to say "while syncing" instead of "while in sync"? "In sync" means that "synchronisation has completed", which is probably the opposite of what you meant to say.