Hello,
I am going to upgrade my server, taking advantage of the fact that I am going to be able to put more hard disks, I wanted to take advantage of this to give a little more security (against loss) to my data.
Currently I have 2 hard drives in ext4 with information, and wanted to buy a third (same capacity all three) and place them in raid5, so that in the future, I can put more hard drives and increase the capacity.
Due to economic issues, right now I can only buy what would be the third disk, so it is impossible for me to back up the data I currently have.
The data itself is not valuable, in case any file gets corrupted, I could download it again, however there are enough teras (20) to make downloading everything a madness.
In principle I thought to put on this server (PC) a dietpi, a trimmed debian and maybe with mdadm make the raid. I have seen tutorials on how to do it (this for example https://ruan.dev/blog/2022/06/29/create-a-raid5-array-with-mdadm-on-linux ).
The question is, is there any way without having to format the hard drives with data?
Thank you and sorry for any mistakes I may make, English is not my mother language.
EDIT:
Thanks for yours answers!! I have several paths to investigate.
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This is madness, but since this is a hobby project and not a production server, there is a way:
- Shrink the filesystems on the existing disks to free up as much space as possible, and shrink their partitions.
- Add a new partition to each of the three disks, and make a RAID5 volume from those partitions.
- Move as many files as possible to the new RAID5 volume to free up space in the old filesystems.
- Shrink the old filesystems/partitions again.
- Expand each RAID component partition one at a time by removing it from the array, resizing it into the empty space, and re-adding it to the array, giving plenty of time for the array to rebuild.
- Move files, shrink the old partitions, and expand the new array partitions as many times as needed until all the files are moved.
This could take several days to accomplish, because of the RAID5 rebuild times. The less free space, the more iterations and the longer it will take.
That is madness. I love it
He said the two drives are mostly full. It’s not a paritioning issue at that point.
Not really with mdadm raid5. But it sounds like you like to live dangerously. You could always go the BTRFS route. Yeah, I know BTRFS Raid56 “will eat your data”, but you said it’s nothing that important anyways. There are some things to keep in mind when running BTRFS in Raid5, e.g. scrub each disk individually, use Raid1c3 for metadata for example.
But basically, BTRFS is one of the only filesystems that allows you to add disks of any size or number, and you can convert the profile on the fly, while in use. So in this case, you could format the new disk with BTRFS as a single disk. Copy over stuff from one of your other disks, then once that disk is empty, add it as a additional device to your existing BTRFS volume. Then do the same with the last disk. Once that is done, you can run a balance convert to convert the single profile into a raid5 data profile.
That being said, there are quite a few caveats to be aware of. Even though it’s improved a lot, BTRFS’s Raid56 implementation is still not recommended for production use. https://lore.kernel.org/linux-btrfs/20200627032414.GX10769@hungrycats.org/
Also, I would STRONGLY recommend against connecting disks via USB. USB HD adapters are notorious for causing all kinds of issues when used in any sort of advanced setup, apart from temporary single disk usage.
Interesting, i think it will be made for my usecase. i’ll check it
Thanks for your answer!!
I’d suggest you move toward a backup approach (“RAID is not a backup”) first. Assuming you have 2x10Tb, get a 3rd and copy half of your files to it, disconnect it, and now half your files are protected. Save, get another, copy the other half, now all your files are protected. If you’re trying to do RAID on USB, don’t, you are already done, otherwise (using SATA or better) you can proceed to build your array in an orderly fashion.
I know its not backup, but, for me, its the sweet point between money and security. Not only for this 2 hard disk, also for the capacity of add more HDs and don’t have all redundancy.
Thanks for your answer!!
Just use Snapraid & MergerFS. No special Hardware required and you don’t need to change what is on your disks.
From a quick search: https://perfectmediaserver.com/02-tech-stack/snapraid/
My recommendation would be to utilize LVM. Set up a PV on the new drive and create an LV filling the drive (wit an FS), then move all the data off of one drive onto this new drive, reformat the first old drive as a second PV in the volume group, and expand the size of the LV. Repeat the process for the second old drive. Then, instead of extending the LV, set the parity option on the LV to 1. You can add further disks, increasing the LV size or adding parity or mirroring in the future, as needed. This also gives you the advantage that you can (once you have some free space) create another LV that has different mirroring or parity requirements.
If all of your data won’t fit on one single drive, you can’t increase your reliability with RAID at this point. You need at least one drive of a size capable of holding all your data to replicate to at least one other drive for RAID 1 at a minimum. Increasing RAID levels from there with replication (not just striping) will only reduce the total amount of space available from the smallest drive capacity in the disk group until you hit a certain number of drives.
Honestly, if you’re wanting to increase reliability for fear of data loss, take a run through your data and see if there’s anything you can ditch (or easily replace later), see how small that data set can be. Revisit RAID combinations after that.
I can recover all, but the time to redownload will be too long :)
