Is it possible to create RAID 5 without losing old data?

Question

NAS

There is a NAS TS-451D QNAP. You need to create data on it, on 2 disks. In a year, it is planned to purchase two more disks and create RAID 5 (3 RAID 5 disks and one spare). Can I make sure that when creating RAID 5, data from 2 disks is not lost? What is the best way to create 2 data disks so that the transition to RAID 5 is possible and minimally problematic?

Thank you.

Answer 1

here they write that it will be possible to expand (provided that at first there was a raid1 of two disks and then you want to make a raid5 of 3 or more disks)
But there the model differs by number, I advise you to rummage through the manuals / interface / ask the manufacturer
ps if I understand correctly algorithm (for example, linux mdadm), then during the migration, the level of disk reliability drops (where raid1 is transferred to the degraded state of raid5 and then disks are added to it), and if something happens at that moment, the data will turn into a mess, and recovery will cost a pretty penny.

If it were a software NAS

на основе linux/windows, я бы советовал вместо одного raid массива на основе дисков, собирать несколько, на основе разделов, разбив исходные диски на одинаковые такого размера, чтобы на него удобно делились текущие и будущие диски, к примеру для 3тб и 4тб дисков я выбрал 1тб раздел.
Благодаря нескольким рейдам, можно вместо миграции просто переносить последовательно данные, пересоздавать массив уже с новой конфигурацией и возвращать данные назад. Я так делал, когда нужно было добавлять по одному диску со временем. Так как это обычное копирование и обычное пересоздание массива, скорость и удобство максимальное и надежность не падает (исключение, если места на дисках не хватает, то приходится сначала копировать данные на новый диск без защиты)

Answer 2

Available NAS ... QNAP

I would strongly discourage experimenting on the combat system in this matter.
We copied the old data, checked that the copy was in order, added disks, created a new array, copied the data to it, checked it again, and continue to work.
Some time ago, we had just US Kunap, who declared the possibility of easy conversion of RAID 5 to RAID 6 (or vice versa - you need to look at the database). The man started. In the middle of the process hung.
We recovered the information, but for the resulting pie of new data, gap-filling, and old data, it was necessary to modify our internal RAID recovery software. It took time and extra money.
So for now, create, for example, RAID 1, use it, and then create a new array from scratch, otherwise you risk becoming our client: https://rlab.ru/raidrecovery/