Lvm and RAID, How?

I have 2 nvme disks, I want to create a RAID 0 but the installer confuses me…

  1. With this manipulation, I will install RL9 on a bare RAID 0, right?

  2. What is here?
    Is it RAID over LVM or LVM over RAID?

  3. Before writing to the forum, I decided to use the help … And what was my surprise that the buttons to be pressed were simply listed there, which I already see. There is no semantic load.

I tried to get out of the “Help” … But how? how? how?
Now I know why the “Reset” button on the system unit.

Please answer my second question, thanks!

Looks like LVM on raid from the images.

The partitioning tool has option to create LVM or standard partitions, with default being LVM. One could probably change that to see how that affects. When creating LVM’s a question is how large the PV partition(s) under it are (use all vs what the LVs need).

LVM is able (or is that deprecated/removed feature?) to stripe or mirror an LV when there are multiple PVs in the VG, but I doubt the installer would use that feature.

that’s what i mean

I think this problem is solved at the operating system installation level, but the installer either does not provide such an opportunity, or does not give a clear understanding of how to do this.
As I already wrote, help does not fulfill its function.

Are you sure you want RAID 0, or do you mean RAID 1

I want to merge the space of two disks.

OK, so you are talking about spanning critical data across two nvme disks?
What if one of the disks fails?

From the screenshot, it looks like it’s already spanning over the two disks, so you could just re-run the installer and agree to it (without going into help this time).

Besides, install is fast to NVMe. One could let it install and then check what the installer actually did.
If the result is what you did want, then you are good to go. If not … now that is more interesting to solve.

The point is good though that the if information is not available up front – before you commit changes – then install is more “luck” than knowledge-based.

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First of all, I see RAID as an increase in read/write speed. I use xfsdump to save data. A server downtime due to a broken disk is not important in my case.

Thank you. Took advice. Installed RL9 with the necessary parameters.
Conclusion: the installer first creates a RAID, and then on top of LVM. Everything works as I hoped.
The speeds are not great ~7000/5000 (R/W), but this is a problem of the disks themselves.

Thanks to all! Problem solved.

I believe device type “RAID” means you’re telling it to create what’s called a “Linux Software RAID”, so mdadm will create a new pseudo-device like /dev/md0 for example which behaves much like any other device.

LVM is not RAID, or at least it’s not branded as such, but it behaves much in the same way as RAID would. If you select LVM, what’s probably going to happen is that it’s going to create what’s called a “Volume Group”, which is a kind of pseudo-device composed of physical volumes (like a disk), that you can then create “Logical Volumes” on which are essentially partitions.

So the short answer is that it’s neither “RAID over LVM”, nor “LVM over RAID”, it’s either or and they are implemented differently.

Creating an LVM on top of software RAID seems completely unnecessary. You’re essentially creating one meta-device to trick LVM into thinking there’s only one disk, when LVM would work just fine with two disks and could stripe it for you.

If I were you I would avoid configuring software RAID at all and simply set up the LVM Volume Group with the “RAID0”-ish configuration as shown in your third screenshot.

edit: actually, it’s possible software raid is actually better in cases where you add new disks for example, at least according to this article, so your mileage may vary.