If you are using SPARCstorage Arrays, note that before replacing or adding a disk drive in a SPARCstorage Array tray, all metadevices on that tray must be taken offline.
In symmetric configurations, taking the submirrors offline for maintenance is complex because disks from each of the two disksets might be in the same tray in the SPARCstorage Array. You must take the metadevices from each diskset offline before removing the tray.
Use the metaoffline(1M) command to take offline all submirrors on every disk in the tray.