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Zoidburgl3r

Member

Registered: 2022-01-18

Posts: 1

LVM2 on top of mdadm RAID10,far2 Disk Failure Fault Tolerance Question

I normally wouldn't make a post about this unless Google, StackOverflow, and the Arch wiki all have proven unfruitful, so here I am trying to get some info on the fault tolerance my newly created RAID+LVM2 main NAS storage has.

Basically, since I have 2 3TB and 2 4TB hard drives, I partitioned both the 3TB drives to use their full capacity, and made partitions with the same amount of sectors on each of the 4TB drives.

I then created a mdadm RAID10,far2 RAID array; then created a physical volume with it, a volume group, and LVM2 using 100%FREE.

What I would like to know, is what exactly is the fault tolerance in terms of a potential disk failure given it is RAID10, but with LVM running on-top of the software/mdadm RAID. I know LVM2 makes it possible to span data across multiple disks with volume groups, but I don't know exactly how LVM2 arranges data on the disk.
What would happen if a single disk failed (that a normal mirrored RAID setup would be able to recover from)?

Tl;dr If I have a mdadm RAID10,far2 array using one partition on each of my 4 hard drives, then made a LVM using that RAID array, what exactly would happen in the event of a disk failure?

Below are the commands I ran to get any info I thought would be relevant and their output:

[drew@NAS ~]$ sudo mdadm -v --detail --scan | sed "s/UUID.*//g"
ARRAY /dev/md/MainRAID10 level=raid10 num-devices=4 metadata=1.2 name=NAS:MainRAID10
   devices=/dev/sda1,/dev/sdb1,/dev/sdc1,/dev/sdd1

[drew@NAS ~]$ sudo pvs; echo; sudo vgs; echo; sudo lvs
  PV         VG         Fmt  Attr PSize    PFree
  /dev/md127 Data       lvm2 a--    <5.46t       0
  /dev/sdb2  DataBackup lvm2 a--  <931.20g       0
  /dev/sdd2  DataBackup lvm2 a--   931.50g       0
  /dev/sde2  system     lvm2 a--  <464.76g <176.76g

  VG         #PV #LV #SN Attr   VSize    VFree
  Data         1   1   0 wz--n-   <5.46t       0
  DataBackup   2   1   0 wz--n-   <1.82t       0
  system       1   5   0 wz--n- <464.76g <176.76g

  LV           VG         Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  DataMain     Data       -wi-ao----  <5.46t
  DataBackup1  DataBackup -wi-ao----  <1.82t
  DockerAndVMs system     -wi-ao---- 120.00g
  home         system     -wi-ao----  60.00g
  root         system     -wi-ao----  60.00g
  swap         system     -wi-ao----   8.00g
  var          system     -wi-ao----  40.00g

Here is also alternatively a screenshot with the details of my current: RAID10,far2 mdadm array, PVs, VGs, and LVMs