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I manage the media archival server for a small photography and graphic design business. We use a five-bay Synology DiskStation 1512+ to archive completed projects and to store TimeMachine backups. I have rebuilt the array a couple of times over the years to replace failing disks and to increase disk size, and I am concerned that my original RAID configuration is no longer appropriate.

The array currently has five new Seagate Ironwolf 3TB disks (ST3000VN007) in a single SHR volume (essentially RAID 5), and it’s my understanding that RAID 5 is insufficient for disks of that size, even with regular data scrubbing. I have a current backup that I can use to rebuild the array, and the volume is currently less than 25% full so there’s a lot of room for extra redundancy. As the server is primarily used for archival, I care mostly about reliability, cost, and ease of maintenance & repair.

What are my best RAID options for a five-bay Synology DiskStation? I could simply continue to use SHR and rely on backups if a resilvering ever fails. I could rebuild the system with SHR-2 (or RAID 6) for an extra disk of redundancy. I suppose I could also switch to RAID 10, but what would I do with the odd disk, a warm spare? How should I weigh the options, and how can I minimize the risk of data loss? The DiskStation does not support conversion of SHR to other RAID types, so I would need to restore from backup to switch.

Bradd Szonye
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    I just saw that the DSM 6.1 update now allows conversion of SHR-1 to SHR-2, but unfortunately it looks like you can only do it when adding a new disk to the array, and mine is already full. – Bradd Szonye Feb 23 '17 at 06:52

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With SHR-2 your entire array is far less likely to fail at once time. SHR (we'll just call it RAID 5) isn't great beyond 1TB disk sizes. For larger disks like that, I'd recommend RAID 6. RAID 10 is overkill that won't necessarily help you in this case since you shouldn't be requiring a lot of random read / write performance from an archive in the first place.

Spooler
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  • Yeah, we were already considering SHR-2, and in researching the details I realized that modern disks are _way_ too big for safety with SHR/RAID5 and that we have been lucky so far to get away with it. I’m kind of surprised that the DiskStation docs don’t make a bigger deal of that. – Bradd Szonye Feb 23 '17 at 04:07