I found this article is quite good.
It is important to store your important data on multiple devices. Data recovery always has the possibility of being unsuccessful and it is not something one should rely on. Data recovery should be considered a last resort, should be used for e.g. attempting to recover that important file you added since your last backup.
I would recommend making sure a backup is up to date before doing a rolling upgrade should you wish to do a rolling upgrade. During a rolling upgrade you have a heightened risk of something going wrong as the level of redundancy is reduced till the array has been rebuilt.
As for multiple layers potentially being a problem, I would recommend downloading the full system logs before and after doing a rolling upgrade. Logs may contain value information should something go wrong (e.g. a disk fails while the volume is not redundant) or partition tables get messed up.
There are ways of obtaining the partition information and/or guessing it based on user recollection of what expansions have been done depending on the severity of the problem, but having logs available which show what state the NAS was in at some recent point in the past is quite valuable.
It is important to store your important data on multiple devices. Data recovery always has the possibility of being unsuccessful and it is not something one should rely on. Data recovery should be considered a last resort, should be used for e.g. attempting to recover that important file you added since your last backup.
I would recommend making sure a backup is up to date before doing a rolling upgrade should you wish to do a rolling upgrade. During a rolling upgrade you have a heightened risk of something going wrong as the level of redundancy is reduced till the array has been rebuilt.
As for multiple layers potentially being a problem, I would recommend downloading the full system logs before and after doing a rolling upgrade. Logs may contain value information should something go wrong (e.g. a disk fails while the volume is not redundant) or partition tables get messed up.
There are ways of obtaining the partition information and/or guessing it based on user recollection of what expansions have been done depending on the severity of the problem, but having logs available which show what state the NAS was in at some recent point in the past is quite valuable.
