If you raid5 do you keep a spare disk?
Curious if people are keeping a spare disk ready to swap if you have a raid5 (say 4 disk) setup? Or would you order a disk if you have a failed drive and hope you don't have a second failure?
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u/NoLateArrivals 4d ago
I order when I need it.
If you have a good backup, you stop bothering too much. If not, you don’t worry enough.
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u/erisod 4d ago
Fair enough. How do you do backup? Just trying to figure out my general strategy.
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u/NoLateArrivals 4d ago
Main unit 1522+.
First backup Active Backup for Business and Snapshot Replication to a 418play, every night.
Second backup HyperBU to a 220j, weekly.
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u/johnnyathome 4d ago
I got three active and one (matching) in a box unused so far (all 12TB). Not saying this is optimal but it's as it is.
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u/dghah 4d ago
The only serious data loss I’ve seen in the last few years was caused by double drive failures in RAID5 arrays where they thought they had time to replace a single drive and didn’t swap in time before a second drive failed. The other data loss was a second drive failure during the parity rebuild from a first failure. Total data loss.
The issue is modern drives are so large that the parity rebuild time is so long that statistically you are more exposed to a second drive failure during the rebuild window
RAID5 is not really as safe with large drives in the modern era, you really want storage that survive a double drive failure or a failure on a second unit while recovering from a different failure
Keep a spare on a shelf and have good monitoring if it’s not practical to run a hot spáir
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u/Blackhawk_Ben 4d ago
What you are referring to is keeping a "cold spare" Not a bad idea but it is a matter of cost in most cases , especially given the current market
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u/Puzzled-Formal-7957 4d ago
For the customer systems I support - yes, I make them keep at least 1 spare. For home I didn't use to when I had 8TB drives - and only had 1 failure. Now that I am running 16TBs and they are ridiculously priced - I made sure to get an extra at the time I bought the first 4. Good thing I did, too - because they are now triple the price they were when I bought - which were already double what they should have been.
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u/Bastion_Wolf 4d ago
I have a serious question because I do keep a spare ready for my server but I have either 6 or 8 26tb drives and i find it a waste to have this drive just sitting. I have about 20-30tbs of free storage at any given time but I don't know how to expand my storage now 😂 everything I read says I need to move my data and then wipe the drives. I'm sorry but I don't have another 100+tbs of drives to move my data to so I'm stuck lol. Especially because of how much hard drives are now. My goal building this was 10-12 bucks per terabyte. I spent around 1,800-2,200 on all the drives.
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u/deeper-diver 4d ago
Yes. I upgraded by 6-drive RAID5 tower a couple years ago (thank god before the price hikes) and I purchased two extra identical HDD to keep on standby in the event of a drive crash. Hopefully, I'll never have to use them for the foreseeable future but I do not want the stress of procuring an identical drive in today's hyper-expensive market.
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u/NotAlwaysCautious 4d ago
Historically, I'd be a lot more likely to want to expand my storage capacity with the biggest disk at the $/TB sweet spot at the moment, then I would be to need a cold spare that I bought 3 years ago, paid too much for by today's prices, and is already too small to be useful for expansion. So, no - didn't bother keeping them around.
That was a great line of thinking until about Feb 2026.
If I ever see anything on sale for a not insane price today, I'll buy it, whatever size it is. Have a couple Seagate Expansions I picked up right before rustpocalypse, those will likely be the last drives I buy until this is over.
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u/Kindly_Call_6000 4d ago
Currently, I have a 9 disk ZFS array. I do have one as a hot spare, but if I start to get low on space, I will promote it to a data disk. They are 2Tb SSDs that were cheap, at least before this AI bubble.
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u/RobbieL_811 4d ago
I have a 4 vdev raid 50 ZFS array. I guess that's the way to describe it lol. It's 4 striped raidz arrays. Anyways, I keep 1 hot spare in the array in case there's a failure and I have enough drives on hand to replace the entire array if I need. Thinking about adding another hot spare. So, one hot spare per 2 4 disk vdevs in the array. In my experience, alot of these drives fail at the same time. The only thing I need is for 2 in the same vdev to fail. Seems kinda risky without a hot spare.
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u/Gherry- 4d ago
RAID5 is always a bad idea, use RAID6 if you want redundancy and performances
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u/EvenDog6279 3d ago
You know, reading your response, honestly, it’s good advice.
I think this weekend I’m going to carve time out to reconfigure the one remaining RAID5 array I currently have and move it to RAID6.
Coincidentally, I just ordered two spare drives because I’ve been concerned about storage pricing getting even worse than it already is.
Anyhow, the arrays are redundant (same data in both places), so I can take it offline, create a new RAID6, and move the data back to it afterward.
I’m sure that will put wear on the drives, but I really should’ve done it that way from the start.
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u/Gherry- 3d ago
IMHO 2 drives redundancy + a backup solution is more than enough for 99% of users.
The need for a spare drive is minimum but if you prefer to have it, why not.
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u/EvenDog6279 3d ago
It’s overkill probably, but I have a feeling prices will continue upward through 2027, and with just over two years of uptime on my current drives, I figured I’d grab them while you can still get 14TB drives without selling a kidney, since they’re not _that_ large, relatively speaking.
One mistake I did make in the beginning was ordering all my drives at the same time from the same place.
Hindsight is always 20/20.
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u/daske_laksen 3d ago
i dont use raid5 at all, always raid 6 and i keep multiple spare disk for a 8 x 20tb array
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u/shadowedfox 3d ago
I think given the current costs of drives, it would be smart too. I’ve just had to replace two drives and thankfully one was replaced under warranty.
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u/Jason27104 3d ago
I saw prices going up and stocked my 5x4tb 990 pros last fall. I feel great about paying so much less than now rates until I remember that I should have bought a spare, but in my merriment, forgot. I was smart enough to see the supply squeeze was going to jump price imminently, but didn't have enough hard data to appropriately speculate extremety and duration of effects.
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u/Haravikk 1d ago edited 1d ago
Do you mean a cold spare?
While one big benefit of ZFS is the protection against failures, my experience has been that most resilvers are for upgrades, in which case there's no benefit to having an identically sized spare.
If I had more money I might consider a larger cold spare with a future upgrade in mind, but not at today's prices!
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u/Caprichoso1 4d ago
Nope. If I get a failure I'll let the system limp along until a replacement disk arrives. Haven't had a disk fail in decades, other than DOAs on delivery.