ADM did not let add to RAID 5 a 4 smaller disk than the previous 3

[calambur]

Now in the system: three disks HGST 10Tb, RAID5. I want to add 4 disk HGST 8Tb in RAID5. ADM drive sees. However, in the RAID control, the add disk button is not active.

[father.mande]

Hi,

Now in the system: three disks HGST 10Tb, RAID5. I want to add 4 disk HGST 8Tb in RAID5. ADM drive sees. However, in the RAID control, the add disk button is not active.

The question is not so precise ...
if you want to ADD a disk to an existing Raid5 but with disks smaller in size ... you CAN'T
if you want to ADD 4 new disks to the existing 3 disks Raid5 (so 7 disks at end) ... create a new Raid5 array with the 4 disk of same size
if you want to REPLACE the 3 disks (10Tb) Raid5 by the 4 disks of 8Tb each
... with A.D.M. I am not sure it's possible ... I don't own large NAS able to build Raid5 ... but on other NAS brand it's not managed directly
... with a full Linux (USB live for ex.) with the correct software ... theoretically (true Linux) you can by resizing the existing Raid5 /dev/mdX device (software) to be able to replace, when finished and verified, existing disk by new disk, now with a low size
... ... it's VERY difficult, and I never test on a NAS ... and it's VERY VERY long to do (especially if CPU and Memory are not high ... )
The best is generally to backup data and restart from scratch OR to know how adding the Raid5 as external disk (in an USB disk box for ex.) and do direct copy to the new Raid

Best in all case is to call the helpdesk (support) ... sure they can help you (or put you in the best way) ... I don't know all the capabilities of large Asustor NAS ... I won only very small (2 disks max.)

Philippe.

[snapshot]

The extra disk must be the same size or larger than the existing ones. So what you are trying to do is not possible and the NAS is acting correctly.