Should I bother with raid
Should I bother with raid
I have a 2 bay NAS, and I was planning on using 2x 18tb HDDs in raid 1. I was planning on purchasing 3 of these drives so when one fails I have the replacement. (I am aware that you should purchase at different times to reduce risk of them all failing at the same time)
Then I setup restic.
It makes backups so easy that I am wondering if I should even bother with raid.
Currently I have ~1TB of backups, and with restics snapshots, it won't grow to be that big anyways.
Either way, I will be storing the backups in aws S3. So is it still worth it to use raid? (I also will be storing backups at my parents)
I always do some level of RAID. If for no other reason, I'm not out of commission if a disk fails. When you're working with multi TB, restoring from a backup can take a while. If rapid recovery from a disk failure is not a high priority for you, then you could probably do without RAID.
Either way, make sure you test your backups occasionally.
Another way to put it: With RAID, a disk failure is like your Check Engine light coming on. You can still drive, but you should address the problem as soon as you can. Without RAID, it's like your engine has seized up and you have to tow it for repair and are without your car until it's fixed.
Hmm that's a good point.
Aws also can cost a good chunk if you restore un-optimally
Keep in mind that if you set up raid using zfs or btrfs (idk how it works with other systems but that's what I've used) then you also get scrubs which detect and fix bit rot and unrecoverable read errors. Without that or a similar system, those errors will go undetected and your backup system will backup those corrupted files as well.
Personally one of the main reasons I used zfs and now btrfs with redundancy is to protect irreplaceable files (family memories and stuff) from those kinds of errors, as I used to just keep stuff on a hard drive until I discovered loads of my irreplaceable vacation photos to be corrupted, including the backups which backed up the corruption.
If your files can be reacquired, then I don't think it's a big deal. But if they aren't, then I think having scrubs or integrity checks with redundancy so that issues can be repaired, as well as backups with snapshots to prevent errors or mistakes from messing up your backups, is a necessity. But it just depends on how much you value your files.
Note that you do not need any sort of redundancy to detect corruption.
Redundancy only gains you the ability to have that corruption immediately and automatically repaired.
While this sounds nice in theory, you have no use for such auto repair if you have backups handy because you can simply restore that data manually using your backups in the 2 times in your lifetime that such corruption actually occurs.
(If you do not have backups handy, you should fix that before even thinking about RAID.)It's incredibly costly to have such redundancy at a disk level and you're almost always better off using those resources on more backups instead if data security is your primary concern.
Downtime mitigation is another story but IMHO it's hardly relevant for most home users.Can you explain this to me better?
I need to work on my data storage solution, and I knew about bit rot but thought the only solution was something like a zfs pool.
How do I go about manually detecting bit rot? Assuming I had perfect backups to replace the rotted files.
Is a zfs pool really that inefficient space wise?
It depends on your uptime requirements.
According to Backblaze stats, you can expect about a 9% probability that at least one of those drives has died after 6 years. Assuming 1 week recovery time if any one of them dies, that'd be a 99.997% uptime.
If that's too high of a probability for needing to run a (in case of AWS potentially very costly) restore, you should invest in RAID. Otherwise, that money is better spent on more backups.
RAID 1 is mirroring. If you accidentally delete a file, or it becomes corrupt (for reasons other than drive failure), RAID 1 will faithfully replicate that delete/corruption to both drives. RAID 1 only protects you from drive failure.
Implement backups before RAID. If you have an extra drive, use it for backups first.
There is only one case when it's smart to use RAID on a machine with no backups, and that's RAID 0 on a read-only server where the data is being replicated in from somewhere else. All other RAID levels only protect against drive failure, and not against the far more common causes of data loss: user- or application-caused data corruption.
I know it’s not totally relevant but I once convinced a company to run their log aggregators with 75 servers and 15 disks in raid0 each.
We relied on the app layer to make sure there was at least 3 copies of the data and if a node's array shat the bed the rest of the cluster would heal and replicate what was lost. Once the DC people swapped the disk we had automation to rebuild the disks and add the host back into the cluster.
It was glorious - 75 servers each splitting the read/write operations 1/75th and then each server splitting that further between 15 disks. Each query had the potential to have ~1100 disks respond in concert, each with a tiny slice of the data you asked for. It was SO fast.
Big elk stack?
And that, kids, is a great use of RAID: under some other form of data redundancy.
Great story!
RAID is 100% about uptime, not backups. If you want less downtime then RAID is your friend.
Having said that, RAID in modern systems is broken and you should use ZFS instead: https://www.youtube.com/watch?v=l55GfAwa8RI
Raid 1 has saved my server a couple of times over from disaster. I make weekly cold backups, but I didn't have to worry about it when my alert came in notifying me which drive went dead - just swap, rebuild, move along. So yeah I'd say it's definitely worth it. Just don't treat raid as a backup solution - and yes, continue to use an external cold storage backup solution as you mentioned. Fires, exploding power supplies, ransomware, etc don't care if you're using raid or not.
It is also useful to stop silent corruption
RAID means that if a drive fails you don't have some downtime while your backups restore. It depends on how you feel about waiting for that.
Also it is easier to hit replace
I want my personal system down until it is back in proper condition tbh
It's up to you. Things to consider:
- Size of data
- Recovery speed (Internet speed)
- Recovery time objective
- Recovery point objective (If you're backing up once per day, is it okay to lose 23 hours of data when a disk fails?)
If your recovery objectives can be met with the anticipated data size and recovery speed, then you could do RAID 0 instead of RAID 1 to get higher speeds and capacity. Just know that if you do that, you better be on top of your backups because they will be needed eventually.
Yes yes yes yes yes
Raid1 that thing and sleep easier. Good on you for having a cold spare, and knowing to buy your drives at different locations/times to get different batches. Your head is in the right place! No reason to leave that data unprotected if you have the underlying tech and hardware.
Yes, I would still do raid. Because a disk fail will not cause a blackout. Much better than have your server offline waiting to replace disk and restore backup.
And no way you can backup 18tb in 1tb, restic or no restic.
RAID is a great backup alternative.
/s
Depends, how much do you value your data? Is it all DVD rips where you still have the DVDs? Nah you don't really need raid. Are they precious family photos where your only backup copy is S3? Yeah I'd use raid for that, plus having a second copy stored elsewhere.
Plus as others have mentioned there's checks on your data for bitrot, which absolutely does happen.
i was also thinking like this, then i had to restore everything from a backup when the ssd suddenly died. I wasted so much time setting everything back as before
If you needed to spend any time "setting everything back as before", you didn't have a full backup.
the reason OP was thinking of doing this, was saving disk space and avoiding buying another hdd. So if it's a 1:1 full disk image, then there's almost no difference with the costs of raid1. Setting exclusions, avoiding certain big files, and so on. In this case he's talking about restic, which can restore data but very hard to do a full bootable linux system - stuff needs to be reinstalled
I absolutely would, for a few reasons:
- restoring from backup is a last resort and involves downtime; swapping a disk is comparatively easier and less disruptive
- it's possible your backup solution fails, so having some redundancy is always good
- read performance - not a major factor, but saturating a gigabit link is always nice
Read perf would be the same or better if you didn't add redundancy as you'd obviously use RAID0.
RAID is never in any way something that can replace a backup. If the backup cannot be restored, you didn't have a backup in the first place. Test your backups.
If you don't trust 1 backup, you should make a second backup rather than using RAID.The one and only thing RAID has going for it is minimising downtime. For most home use-cases though, the 3rd 9 which this would provide is hardly relevant IMHO.
Read perf would be the same or better if you didn't add redundancy
RAID 1 can absolutely be faster than a single disk for read perf, and on Linux it is tuned to be faster. It's not why you'd use it, but it is a feature of RAID. Intuitively, since both disks have exactly the same data, each disk could read different things. Likewise, for writes, you don't have to write at the same time, as long as they're always correct (e.g. don't flip the metadata segment until both have written the data), so you can even get a write boost.
If performance is all you care about, then yeah, go ahead and use RAID 0. But you do get a performance boost with mirroring as well.
Yes, a backup should be tested, but it shouldn't be relied on. Internet can go down, services can have maintenance, etc, so it's a lot better to never need it. If you can afford a mirror, it's having.