ONTAP Discussions

Spare Disks



We have FAS 2750 system running in HA with 1 external DS224C attached(only 12 drives are populated and 12 are free). 2 data aggregates are running on Raid DP, one on each controller. Aggregate 1 has 1 Raid Group, Aggregate 2 has 2 Raid Groups out of which 1 Raid Group has no spare drives. Both Aggregates have dedicated spare drives though.

Now my concern is what will happen if a disk failure will occur in the Raid Group with no Spares? Will it still continue working considering the fact Aggregate has spare drives.

I was looking at ONTAP Documentation which says, "A Single Spare Disk can serve as a hot spare for multiple Raid Groups". I would appreciate if someone can explain and clear my doubts. Attached image from ONTAP Documentation Center.


Asif Ali



In FAS, A hot spare disk is a disk that is assigned to a storage system and is ready for use, but is not in use by a RAID group and does not hold any data.




In short: Hotspare is not assigned to RAID_GROUPs/Aggregates, rather it is assigned to a storage system (Physical Node). It is available to be used/picked-up by any raid-groups (When a disk in that RG fails) as long as there is a matching spare type available on the Node where the Aggr(raidgroups) exits.


So does that mean if I have enough spares on a Node, I can breathe easy.

It doesn't matter if a Raid Group exists without any dedicated spares. As long as there are spares on a Node, life is good.

Please correct me if i am wrong.


Asif Ali


Yes, your understanding is correct. As long as there are online good spares of the matching disk type on the Node, you can breath easy 🙂

Thank You

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