A friend got a new server with 8 HDDs, he created a raid5+1 hot spare. and installed the os. after that he wanted to test whether the hot spare would would and he pulled a disk from raid5. successfully the hot spare was added to the raid5 and rebuilt the raid5.
Now the question is that the HDD he earlier pulled; he wants to put it back and use as the new hot spare. since there is some data in this HDD since it was participating in the raid5 earlier, will this work as hot spare? or else will he have to format this disk? if so, how to format? from ACU?