Model backward compatability

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Larswad
Posts: 2
Joined: Mon Aug 07, 2017 9:31 am

Model backward compatability

Post by Larswad » Mon Aug 07, 2017 9:52 am

I am not sure if this is stated anywhere else, tried searching but haven't found an answer.

Beside the issue of a drive failing in a RAID5 system (which of course is remedied by replacing a failed drive during degradation), the possibility of the NAS hardware itself failing is a clear possibility.

I have the NAS540 with a RAID5 configuration. The NAS540 is not possible to buy anymore in my country (Sweden) and it seems to go out of stock everywhere else.

The 542 seems to be the close successor, but is the hardware drive file system format compatible with the 540?
The natural thing would be to simply move the drives from the old nas to a new one and simply switch on the power.
My guess is that this would/should work, but I would like to have that confirmed by Zyxel themselves.

Also, for any future models, is there a spoken commitment by Zyxel to always be backward compatible with the drive file system and configuration?
I do understand that the NAS must be able to carry at least the same amount of drives.

Finally, if I would ever run into trouble where the NAS cannot be replaced, what is the actual file system used by NAS540? Is it ext3 or ext4 or something exotic? Can I simply mount it in a PC-based RAID5?

Mijzelf
Posts: 6205
Joined: Mon Jun 16, 2008 10:45 am

Re: Model backward compatability

Post by Mijzelf » Fri Aug 11, 2017 7:24 am

The 542 is technically identical to the 540. I think they introduced a 'new model' because the 540 was able to have a volume >16TiB, which vanished in firmware 5.10. (Long technical story). The 542 is limited to 16TiB from the beginning.
So yes, it should work. (Unless you have a >16TiB volume, in which case you have a real problem if your box fails. A PC won't mount the volume either.)

There is no guarantee on backwards compatibility, but I think it will be compatible for some time. All disks from all NAS models have been exchangeable since firmware V1.0, back in 2006/7. With the transition to firmware 5.0 the compatibility with older firmwares is dropped. If you extrapolate that, you should be safe until 2023/4.
what is the actual file system used by NAS540? Is it ext3 or ext4 or something exotic?
Ext4
Can I simply mount it in a PC-based RAID5?
Depends what you mean with PC-based RAID5. It won't work with some hardware raid controller AFAIK, but if you can connect 4 disks to a simple sata controller, you can use Linux software raid, which will work fine. (Unless you have a >16TiB volume. The array will build fine, but you can't mount the volume. In that case you'll have to search for fuse ext4.)

Larswad
Posts: 2
Joined: Mon Aug 07, 2017 9:31 am

Re: Model backward compatability

Post by Larswad » Sat Aug 12, 2017 10:37 am

Thanks!
Very satisfying answer! I feel much safer now, even beyond some 10+ years since I can always mount them then under Linux with software raid and move to a new NAS. And 16TiB is not an issue for me, I have three 3TiB's.

I noticed there was a different cpu architecture in the 540, but maybe it has equal performance.

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