Hello Ken, You can replace drives from different manufactures.  The thing you need to know is that the drives need to have Isilon firmware installed on them in order for your system to see the drive.  Any drive that doesn’t have Isilon firmware will not be seen, as the firmware is loaded on the drive at the factory.
HiI got one HDD failure in my isilon X410. Initially is using hitachi brand. Can I use seagate or WD drives to replace it?     ThanksKen
Use other brand HDD to replace