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this post was submitted on 24 Aug 2023
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RAID is something I haven’t learned yet but really should.
My server has 4 4TB hard drives. Sounds like I could do RAID10 and only have 4TB of storage. Or RAID5 and 8TB?
Right now I have no raid. 1/4 of my hard drives has about 700GB of data and is movie and shows. 2/4 hard drive has 91GB and is photos and cloud data. 3/4 is blank and 4/4 is borg backups from my desktop and server and second hard drive currently at 120GB. My media drive has no backups right now and is not really being used.
It sounds like I could put all of my data on hard drive 1 which will only be about 1TB and then have RAID so that data is secure.
I would like having 8TB storage with raid 5. But maybe raid 10 is smarter and if I want more storage I’ll have to get more drives.
With RAID10, you’d have 8TB of storage that is both striped and mirrored. You’d get a 4x increase in read speed and a 2x increase in write speed. You’d be fault tolerant against AT LEAST one drive failure, possibly two depending on which drives fail.
With RAID5, you’d have 12GB that is striped and parity checked. You’d get a 3x read speed increase and normal write speed. You’d be fault tolerant against a single drive failure.
With RAID6, you’d have 8TB that is striped and parity checked. You’ll have a 2x increase in read speed and normal write speed. You’ll be fault tolerant against two concurrent drive failures.
I recommend RAID10 if you want the all around speed boost and fault tolerance but don’t care so much about capacity;
RAID6 if you care more about redundancy;
RAID5 if you want a read speed boost and more capacity with a little fault tolerance mixed in.
There’s also raid 0, which is gonna be hella fast all around but god help you if somebody farts too aggressively next to it; and raid 1 if you just want 4 redundant backups of the same drive.
Personally, I’d go 10 unless you just really want the extra storage.
Wow thank you for the detailed response. After reading through it i think I agree with raid 10 being my best option. Gonna start reading into it more and how to set it up! These hard drives aren’t new so being safe against at least one drive failure sounds safe. Can easily replace one if it goes out. Hopefully 2 don’t go out at the same time but it looks like I potentially will still be safe if so.
Iirc your storage is halved with raid 10, not quatered.
Be wary of RAID 5 or 6.
They both have a « write hole » problem (or though much less so in RAID 6). Any power failure which causes an incomplete write can cause a complete RAID corruption - meaning all data is lost. Hardware RAID controllers usually have an onboard backup battery so they can store some information to complete operations should there be a sudden power failure. Software RAID does not have this, and you need to provide a UPS with automatic clean shutdown as the battery runs low using nut or some equivalent.
Some people go as far as to say that RAID 5 should never be used.
You also have very long recovery times when you replace a failed drive (days). Any other failure during this time means total data loss (of course RAID 6 gives you a second redundancy). Weekly Resyncs are very slow too (hours to days), and (unless you constrain your max throughput) will bring your system to its knees.
zfs does not suffer from these problems, BTW.
I run software RAID 5 via mdadm and have a UPS. I’ve replaced drives twice with no issues other than a slightly nervous long wait during recovery. I’m too cheap to buy the extra HDD for RAID 6, and may end up regretting it one day.