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by ryao 517 days ago
You can use different sized disks, but RAID-Z will truncate the space it uses to the lowest common denominator. If you increase the lowest common denominator, RAID-Z should auto-expand to use the additional space. All parity RAID technologies truncate members to the lowest common denominator, rather than just ZFS.
2 comments
wrboyce 516 days ago
Is it definitely the LCD? Given drive of size 15 and 20 the LCD would be 1, no? I had assumed it would just use the size of the smallest drive on every drive (so 15+20->15+15=30). When I first read your comment I was thinking of GCF but even that would be fairly inefficient (GCF(15,20) = 5, so 15+20->5+5=10).
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GauntletWizard 517 days ago
That's not entirely true, Unraid has mechanisms for unbalanced disks, but they come at a high cost in terms of usability by standard workloads.
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ryao 516 days ago
Unraid is not a RAID technology:

> Unraid saves data to individual drives rather than spreading single files out over multiple drives

https://en.wikipedia.org/wiki/Unraid#Software-defined_NAS

At least, it is not one in the sense of the original RAID paper that coined the term:

https://web.mit.edu/6.033/2015/wwwdocs/papers/Patterson88.pd...

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