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Make a raid 5 with two almost full disk and another one empty (lemm.ee)

submitted 4 months ago* (last edited 4 months ago) by [email protected] to c/[email protected]

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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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[–] [email protected] 3 points 4 months ago* (last edited 4 months ago)

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.