Referencing: https://lemmy.world/post/17588348
I want to make a NAS with a 500GB boot drive and 2x16TB HDDs. Based on my previous post, btrfs is a good option. It also looks easy to get started. My plan for the NAS would be to purchase several 16TB drives, and only use 2 of them.
My first question is about different drives. Could I purchase two different brand drives and use them with btrfs? (I assume yes)
2nd question: how does the replacement process go? Like if drive A died, so I remove it, and put a brand new replacement in. What do I have to do with btrfs to get the raid 1 back going? Any links or guides would be amazing.
My first question is about different drives. Could I purchase two different brand drives and use them with btrfs? (I assume yes)
You can.
2nd question: how does the replacement process go? Like if drive A died, so I remove it, and put a brand new replacement in. What do I have to do with btrfs to get the raid 1 back going? Any links or guides would be amazing.
Depends on what NAS/Software you have. If your NAS supports hot-swaps you can just pull out the defective drive and plug in another. Otherwise you’ll have to shut it down, swap the drive and turn it back on.
If you have already have the spare drive ready and you have slots availible, you can run a “hot spare”. This way you can even start the raid rebuild if you’re not physically near your NAS (like when a drive fails while you’re on holiday or sm).
Hm okay. I was thinking of using Debian and likely a 4 bay case.
So the process for a dead HDD: Power off. Pull out dead drive and replace. Power on. Now what? Does Debian/a specific motherboard support auto rebuilding the raid 1? Or what are the commands to rebuild?
I’m using Synology/DMS and there you have a pretty neat GUI that lists newly detected drives and let’s you assign them to your storage pool and rebuild the raid. I’d expect it to be quite similar on software like TrueNAS Rockstor.
Btrfs has it’s own build-in raid. From what I understand you should mount the filesystem with -o degraded and then use btrfs replace to switch to the new drive. I’ve never had to do that myself yet though.
In days past some drive vendors had different sector layouts for drives and would cause issues with raid. Pretty sure most nowadays are all the same layout and you won’t run into any issues. I still look to get the same drive model anyways just to be perfectly sure that there are no issues.
Even then you may run into weird issues like one of my 1.2 TB enterprise ssd drives was reporting 1.12 TiB rather than 1.09 TiB the other 7 drives had. TrueNas refused to build a vdev with that drive and I had to return it to get a new one.
Is btrfs RAID stable yet? This article is three years old, so maybe things have improved, but it contains some pretty strong warnings about the dangers of btrfs RAID:
https://arstechnica.com/gadgets/2021/09/examining-btrfs-linuxs-perpetually-half-finished-filesystem/
To summarize, the article argues that btrfs is great for single-disk usage but its RAID implementations are idiosyncratic and unreliable.
(I use btrfs daily on several single-disk computers and it has been great, but I have never tried its RAID.)
I believe it’s only RAID 5 and 6 that are unstable, https://btrfs.readthedocs.io/en/latest/btrfs-man5.html#raid56-status-and-recommended-practices
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I’ve seen in this thread:
| Fewer Letters | More Letters |
|---|---|
| NAS | Network-Attached Storage |
| RAID | Redundant Array of Independent Disks for mass storage |
| SATA | Serial AT Attachment interface for mass storage |
| SSD | Solid State Drive mass storage |
| ZFS | Solaris/Linux filesystem focusing on data integrity |
5 acronyms in this thread; the most compressed thread commented on today has 9 acronyms.
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This is a good guide: https://wiki.tnonline.net/w/Btrfs/Replacing_a_disk
Usually you want to replace drives before they fail (SMART monitoring will give you ample warning in most cases). The it is better to have an additional free SATA port to turn the failing raid temporarily into a three-way raid and use the btrfs built-in function to replace the disk in situ.
