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I have a Synology 4-bay NAS (RS409RP+) with a RAID 5 installed on 4 hard disks. Now I need to upgrade the NAS to a bigger set of hard disks, and because these hard disks are 3TB each, I cannot use the normal RAID upgrade function. Of course I am going to make a backup and migrate the data over to the new disks, but I would like to keep the old disks functioning in the meantime, so if something goes wrong, I can reinsert the old four disks and continue as normal.

My question is, when I shutdown the Synology NAS and remove ALL of the disks, is it possible to re-insert them again later in the same order and will they still function normally?

Or does the NAS keep some information about the internal hard disks somewhere else (e.g. in the bios or an internal flash memory) and will it report that the raid has failed when I insert the old disks again? Or will it know that I have inserted some other disks in the meantime?

According to my understanding it shoud be save, but before I attempt this, I would like to know if someone has some definitive experience with this?

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I don't see why not, but RAID5 with disks more than 2TB may cause issues when trying to rebuild an array. – tombull89 May 17 '13 at 14:39
So you recommend to build a RAID 1 or RAID 10 with this NAS? – lanoxx May 17 '13 at 14:41
If I had 4 3TB disks, then yes, I would go with RAID10, or RAID6 if the device supported it. – tombull89 May 17 '13 at 14:54
Agreed with tombull89. If you need good write performance, go with RAID10. RAID6 is more resilient, on the other hand (it looks like the RS409RP+ does support it). But, of course you'd have ~6TB usable rather than ~9TB w/RAID5. – May 17 '13 at 20:09

Yes, I have done this. At least, I have removed all the drives, and put them back in, and powered up without data loss. I have not swapped drives in the middle.

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up vote 0 down vote accepted

This is the response from the Synology Support:

When the DS is powered off, if you just remove all the HD temporarily and insert
all of them in order again, all the data in the HD (DSM operating system and your data)
will still exists, unless there are already seriously bad sectors on the HD.

So it should be no problem, unfortunately I have not yet had a chance to try this myself.

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Get out your felt marker and number each one to its position so they can be reinserted in the proper order. – Fiasco Labs May 25 '13 at 18:49

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