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I'm looking for something redundant I can just plop on a server with a bunch of garbage drives that just works without the smaller drives crippling the capacity of the larger drives.

Lets say I have four drives of unequal size because I am poor. If I understand right, this is how it would look under RAID 5:

enter image description here

There are 9 GB of actual stored data

But, does something like this exist?:

enter image description here

There would be 12 GB of actual stored data

Also, is there a storage method that allows one to have redundancy, but also the ability to grow a pool of drives by just adding more storage? I'd like to grow my server without having to completely rebuild it (again, poor).

Thanks

  • Ive not played with it, but look at lvmraid - this uses the flexible LVM disk management framework to do RAID. Also, dont use RAID5 for more then 2TB of data as its not considered reliable due to the risk if a second failure due to rebuild. – davidgo Jul 24 at 8:16
  • Your second illustration looks odd to me. Shouldn’t the last row be F1, F2 and FP? – Scott Jul 25 at 3:13
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To make the most use of space, it might be an option to create a raid-5 with the first 3gb of all 4 drives, then create another raid 5 for the remaining 2gb on the 3 5gb drives and combine both raids in a raid 0 (striped). Expanding the raid 5s would be impossible however, so the only option for expansion is to add a (virtual/physical) device to the parent raid 0.

To try use all drives and still allow expansion, you could split the drives into two groups with a total capacity as equal as possible, create an expandable raid 0 (striped) for each group, and then implement a raid 1 (mirrored) system with the two raid 0 systems. This could even work for raid 5 with 3 or more groups, as long as you can group them appropriately. Expanding this would mean adding a drive to all groups, expanding their raid 0 systems, and then expanding the parent raid to use the new space. While easy on a fundamental level, the last step could prove challenging in practice.

Honestly, this all just sounds like headache. I think your best option is to pair drives of the same size, create a raid 1 (mirror) with each pair, and have an expandable raid 0 (striped) implementation such as ZFS pools to put them into one device. You might not use all the drives, and you can only add two drives at a time, but it's simple, expandable, easy to understand and quite redundant.

Striped/mirrored ZFS pools (https://www.freebsd.org/doc/handbook/zfs-zpool.html)

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If you are using Windows, it would be possible with Storage Spaces on Windows 8.1 and higher. See:

https://serverfault.com/questions/770472/mixing-disks-of-different-sizes-in-a-storage-spaces-pool/771293#771293

https://www.pcsteps.com/738-software-raid-windows-storage-pools/

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