We have a Netgear ReadyNAS 424 with 2 harddrives with raid1. We have a capacity problem and we want to add 2 disks to this raid system, so we want to total 4 disk drives work with raid1. I didnt find a clear explanation for this incident. What steps should I follow, thanks..
We have a Netgear ReadyNAS 424 with 2 harddrives with raid1. We have a capacity problem and we want to add 2 disks to this raid system, so we want to total 4 disk drives work with raid1.
The NAS doesn't support 4 disks in one volume as RAID-1 - and that would not increase your capacity. RAID-1 is mirrored disks, and 4 mirrored disks has the same capacity as a single unmirrored disk.
Is the NAS using XRAID? You can tell by looking on the volumes page in the NAS admin UI. If you are using XRAID, there will be a green stripe on the XRAID control on the right of the page.
What disks do you have in the NAS now (manufacturer and model please)?
Step one is to make sure your backup is up to date. While expansion is usually flawless, unexpected things like a drive failure during sync can cause data loss.
Then all you need to do is add one more drive that's at least 10TB in size. A drive of similar rotation speed is recommended. It is best to do that with power applied. That new drive will cause the NAS to switch your RAID to RAID5 and begin syncing the new drive into that RAID. When it competes, you'll have an additional 10TB of storage. If you added a drive larger than 10TB, the additional space will be unavailable until it has a drive large enough for it to create another RAID.
Since 10TB has been enough for you up until now, I recommend you stop here with 20TB. If you wait to install the 4th, then that drive won't be the same age and is less likely to fail at nearly the same time.
But when you do finally add a 4th drive the same size as the 3rd, the RAID will expand to a 4 drive RAID5, growing another 10TB. If the 3rd and 4th drive were larger than 10TB, then the additional space on them will create another RAID1 and that will be added (seamless to you) to the available space. Since it's a RAID1, then the added raid will have half the size of the added space. So if the last two added were 16TB, you'd end up with the main 30TB RAID5 and a 6TB RAID1 all tucked into one available volume.
(FYI, I didn't see @Sandshark's reply until after I'd posted this. My reply includes my recommendation to test the disks before deploying them, otherwise they are substantially the same).
First of all, the capacity rule is "sum the disks and subtract the largest". When replacing disks you want to either replace a disk with one of the same size, or replace it with a disk that it at least as large as the biggest disk in the array.
Right now you have a 10 TB (~9.09 TiB) volume. Adding one more 10 TB disk will double the volume size to 20 TB (~18.2 TiB). Adding two will triple the volume size to 30 TB (~27.3 TiB). Note if you added 16 TB drives instead, the first disk would still increase the volume to 20 TB, but the second would increase it to 36 TB (~32.7 TiB).
I recommend either Seagate Ironwolf disks or enterprise-class disks. (WD Red Plus or WD Red Pro would also work). I always test the disks in a PC first using vendor tools (Seatools in the case of Seagate). With Seatools I run the full non-destructive test, followed by a full write zeros test. I run both because I have sometimes purchased disks that pass one of these tests, but fail the other.
Netgear recommends ensuring that you have an up-to-date backup before manipulating disks, and I agree with their advice. The array is not protected during expansion. Hot-insert one disk (NAS running) and wait for the expansion to complete. Note the NAS will convert the volume to RAID-5 (X-RAID) during this step. Then add the second disk (assuming you need two).
You can use the NAS during the expansion process, but performance will be slower than usual.
