If a disk fails and no hot spare disk that exactly matches the failed disk is available, Data ONTAP uses the best available spare.
Data ONTAP picks a non-matching hot spare based on the following criteria:
- If the available hot spares are not the correct size, Data ONTAP uses one that is the next size up if possible.
Note: The replacement disk is downsized to match the size of the disk it is replacing; the extra capacity is not available.
- If the hot spares are not the correct speed, Data ONTAP uses one that is a different speed.
Note: Using drives with different speeds within the same aggregate is not optimal. Replacing a disk with a slower disk can cause performance degradation, and replacing with a faster disk is not a cost-effective solution.
- If SyncMirror is in use and the hot spares are not in the correct pool, Data ONTAP uses a spare from the other pool.
Note: Using drives from the wrong pool is not optimal because you no longer have fault isolation for your SyncMirror configuration. Warning messages go to the logs and console to alert you to this issue.
- If the hot spares are not the correct type (FC, SAS, SATA, or ATA), they cannot be used as replacement disks.
- If the hot spares are ZCDs, they can be added only to zoned checksum aggregates. ZCDs cannot be added to block checksum aggregates.
