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Situation is: 1x1TB 7200 HDD; 1x0.5TB 7200 HDD; 1x1TB 5400 HDD; 1x0.5TB 5400 HDD. All interconnects SATA3.0+

Desired outcome... Join the 2x 500GB HDDs to form 1TB; Present that to LVM as 3x1TB volumes for striping.

How would LVM handle striping with 2x 500gb volumes, along side 2x 1 TB volumes? Presumably defaults to linear on the 500s, meaning one drive wont even get used until 1.5T of data is written? and in such case, would drag the array down to that speed?

I am going to "give it a crack" over evenings this week, but if anyone has any input, pitfalls etc, all useful advice gratefully recieved. If it's practicable then I will do the same with 2x2T + 4T

user497028
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    Instead of doing this, why not use MDADM RAID0 on the 2 500GB HDD's and present them as a single disk to LVM? – davidgo Aug 14 '23 at 09:21
  • Nested LVM is certainly possible (link), but perhaps for other purposes (link). Stacking LVM volumes might be related. – harrymc Aug 14 '23 at 09:28
  • @davidgo - Thanks, I will read more into mdadm, but it seems to be adding another layer of abstraction since it's all being managed in software. Do you think there would be a notable performance penalty in doing so? Drives are also dm-crypted, if that makes a difference. Alternatively do you think mdadm could meet my requirements by itself? – user497028 Aug 14 '23 at 14:40
  • @harrymc - Thankyou, I'm not sure why my google-fu failed to turn up any of those links but I will read through them. – user497028 Aug 14 '23 at 14:42
  • With Linux disks its almost a case of "turtles all the way down". I don't know what you are ultimately trying to achieve, but a formula that works well for me is to use mdadm or hardware RAID to shape my raw disks, then use LVM to get flixibility of managing partitions and snapshotting. For RAID/RAID Like semantics I would always be inclined to use MDADM rather then LVM (MDADM is definitely simpler and by most accounts faster then LVM RAID). It likely also has advantages if you need to recover/replace disks. – davidgo Aug 14 '23 at 21:04

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