SHR on two identical disks

The set of questions from here, while SHR-specific, applies to NETGEARs X-RAID as well.

I have a DS213j set up as Synology Hybrid RAID (SHR) with 2 2TB disks. What happens if the DS213j fails? Are the disks just mirrors so that I can connect either to a PC and see it as an external drive and recover the data? If not would it be better to change to RAID 1? What are the advantages of SHR over RAID 1?

SHR means Synology Hybrid RAID. The advantage of SHR is that SHR can better utilize capacity of mixed size disks, and SHR supports some weird disk upgrades which are normally done by deleting and rebuilding the traditional array.

However, if we are talking two identical disks and no plans to upgrade, SHR is in effect the same as RAID1, so there is really no choosing one or the other.


Synology SHR

Recovery of a crashed volume on a Synology (here), can be complicated if SHR is involved,

I have a DS1010+ with all five drives composing a single SHR (Synology Hybrid Raid) volume.

I had a fan go bad … which seems to have corrupted the volume. Currently the volume reads as “Crashed” and two of the five drives read as “System Partition Failure”. … S.M.A.R.T. Test … resulted in “Normal” readings.

… has anyone has had success recovering data from a crashed volume that used SHR vs. a more universal RAID format. Or could anyone suggest a data recovery process or software that might work with SHR.

As far as the disks are installed all at the same time, and all the disks are identical, Synology Hybrid RAID is the same as normal RAID5. If one more disk of the same size is added, the array is expanded but still conforms to a RAID5 spec. If the disks are replaced with larger ones to expand capacity, the SHR capabilities come into play and the array does not conform to a RAID5 spec any longer.

One way to deal with that is to call Synology support and have them try and fix the issue. The other option is to use our Home NAS Recovery, but it will only work with SHR if all disks are of the same size and all were installed at the same time.