Oof. I've got a NAS with 4 3TB Seagate Barracudas, same model number as the drives with the 46% failure rate. One's already failed, and I replaced it with the same model drive.
Anyone have a recommendation for how to replace all the drives with more reliable models without wrecking the RAID? Downtime is okay, but I don't have spare space for the contents to make a giant backup. It's currently set up as a "Synology Hybrid RAID" that looks an awful lot like a RAID 5.
Without a backup, you need a temporary, identical NAS device with the 4 new disks. Then do a file-level copy. Then put the 4 new disks in the old NAS and import the array. Do you know of a store with a very lenient returns policy?
An online capacity expansion (replacing one at a time) will mean a very long time in a degraded state, possible multiple disk failures, increased chances of data loss (power goes off, etc)
If you have a spare PC lying around, check out the XPenology forums [1] for the software (specifically, NanoBoot or XPEnoboot) required to create your own Synology clone.
You'll be able to create a new SHR volume with new disks. As suggested in another post, do a file level copy to the new volume. You should then be able to replace all the disks in your actual Synology NAS with your new disks at once, and perform a migration [2] so everything works with your Synology hardware.
(This is possibly a better solution than replacing the disks one by one, since there's the risk of another disk failing while the RAID is being rebuilt.)
HGST drives are slightly larger than Seagate of the same advertised capacity. Replacing Seagate drives with HGST ones is therefore easy, while it's often impossible the other way around (fortunately :)
How full is your NAS? If you're not that full and your data could fit on one non-RAID hard drive, you can add a 4th drive as a second disk group, copy folders manually in Diskstation to the 4th drive, then pull the other three, create a new 3-disk disk group there, copy back once that's built, then wipe the 4th and add that. That's convoluted but for me was the easiest and most reliable way. With the RAID max_speed tweaks, it was all done in about 72 hours end to end.
If the NAS uses linux RAID you just need drives that are AS LARGE or LARGER than the current drives. Precisely, not what's marked on the box. If you want to be on the super safe side and are uncertain, get somebody to help you DD(or dcfldd) each old drive onto a new drive and then just pop the whole new set into the NAS and let it rip.
It would also be a good idea to check the NAS vendors forums.
Anyone have a recommendation for how to replace all the drives with more reliable models without wrecking the RAID? Downtime is okay, but I don't have spare space for the contents to make a giant backup. It's currently set up as a "Synology Hybrid RAID" that looks an awful lot like a RAID 5.