Re: [EXT] [qubes-users] RAID6 as secondary storage and thin pool

[Ulrich Windl]

On 5/5/21 12:56 AM, Thorsten Schierer wrote:
> I'm currently evaluating the possibility of moving my workstation to
> Qubes OS and ran into a problem.
> It's using an SSD for Qubes OS, but I want to use HDDs with RAID6 to
> hold qubes data.
> I've been using the secondary storage guide and slightly altered it for
> RAID6:
>
> I ran "sudo cryptsetup luksFormat --hash=sha512 --key-size=512
> --cipher=aes-xts-plain64 --verify-passphrase /dev/sdx" for 5 test HDDs.

I'm not an expert on this, but why do you cryptsetup each HDD instead of
cryptsetup the RAID device? The data on HDD still should be encrypted. ;-)

> Then I added their UUID to /etc/crypttab and rebooted.
> After than I ran "sudo pvcreate /dev/mapper/luks-[UUID]" for the 5 drives.
> I created a volume group with "sudo vgcreate qubeshd0
> /dev/mapper/luks-UUID1 /dev/mapper/luks-UUID2 ...."
>
> Then I did this:
>
> sudo lvcreate -i 3 --type raid6 -L 10G -n poolhd0 qubeshd0
> sudo lvconvert --thinpool qubeshd0/poolhd0
> sudo lvextend -l +100%FREE qubeshd0/poolhd0
>
> This seems to give me a RAID6 thin pool with the correct size. I created
> VMs and used this pool for data storage and everything seems to work
> fine. So far so good.
> After that I wanted to go through some other scenarios like adding HDDs
> to the RAID (growing it) or replacing faulty hdds.
>
> I was able to add a new HDD to the volume group but after that I got
> stuck, since I was unable to add the new free space to the RAID6.

You want to extend the RAID, , i.e. the PV, not add a single HDD as PV,
right?

> Everything I tried gave me an error. One of them was that thin pool did
> not support the operation. I also tried it without converting to thin
> pool but still was unable to extend the RAID6.

I think you must reserve "RAID slots" (number of disks to expect" when
creating the RAID. Maybe you can tune that later, but I'm unsure.

>
> Things like this are the reason why I wanted to simulate/evaluate
> everything first before actually moving everything.
>
> How can I extend the 5 hdd RAID6 to 6 hdds (and higher)? Over time the
> final target would be to grow the RAID to around 10-12 HDDs.
> Was that even correct how I implemented it? What would be the best way
> to accomplish it?
>
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