tech: Wait for Synology rebuild, SHR2 > RAID6 and Drive Order matters

OK, we finally have things in place and we’ve been copying files from an older SHR (Synology Hybrid RAID) system to a newly created SHR2 (this allows two levels of redundancy).

The problem is that for the first week, I was only seeing 100MBps transfer rates, but the underlying disks were running at 600MBps. Well, the “optimizing” disks finally stopped and the next copy is 600MBps.

Lesson: When you create a new SHR2 or other storage pool, let the thing settle out. It takes days with these massive drives to build parity and so forth. Rebuilds can take months if you are not careful, which is a good reason even for a new drive array to wait it out.


I normally use matched drives and don’t like using proprietary data formats. But, SHR2 does allow you to gradually upgrade arrays, so if you have a 12-drive array, this is not such a bad thing. The good news is that it turns out SHR2 is not that custom. They are creating logical volumes on the disk and then stitching those into a RAID array. Problem solved, if you have fewer than eight disks, SHR is your friend. If you have more, then SHR2 is.

Why these figures, well it’s about how much real storage you get. With 8 disks, SHR2 will leave you with 6 real drives or 80%. But if you have 8 disks, you only get 50%.

Drive order matters on boot keep old ones at top, one no-2FA account

One thing that isn’t super clear is that every Synology NAS has a hidden system partition on every disk. The idea is that if you have only one disk left, you can still boot the system. This works pretty well unless you swap drives around. What happened to me was that if you put a drive array in drive 1, then the thing can get confused particularly if you have 2FA turned on. Now all the keys are out of date, so three fixes to this:

  1. When you are moving disks around, make sure the working drives are at the “top” that is in slot 1 so that it boots properly.
  2. You should have at least one account (with a gigantic secret password) that has 2FA turned off. This is because the users are stored on these system partitions and you can at least recover. Otherwise, you have to reset the operating system which is painful.

And please don’t make that account “admin” as if you get hacked, they will focus on that user name. It is cool that Synology disables admin by default.

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