  You could do it either way, but for the sake of simplicity I would power down. If you remove the disks while they are powered up then the controller will see the removal and start marking the drives as failed. If you need to reinsert the drives you would have to deal with foreign configurations and rebuilds if you remove them while the server is online. If you remove them while the server is offline then you it will be easier to bring the drives back online if you need to put them back in to recover data. You do not need to offline the drives if you remove them while the server is off. If you decide to remove them while the server is on then I would offline them until the array goes to a failed state. Thanks
I have a Raid10 data array in a T710 that needs to be replaced/rebuilt with larger drives. I have a total of six drives in the array.  The controller is a PERC 6i integrated controller.  After I have a verified backup, what is the best method for removing the existing array and replacing it with a new one?  Is it okay to do this using OMSA since it is not the boot array or is it better to use the PERC BIOS utility?  Thanks.
Best practice for replacing a RAID10 array