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Ency
Asked: 2011-01-01 04:55:36 +0800 CST

What is better LVM on RAID or RAID on LVM?

  • 772

I currently have LVM on software RAID, but I'd like to ask you what you think it is better solution, maybe some pros and cons?

Edit: It is about software raid on lvm or lvm on software raid. I know than hardware raid is better if we are thinking about performance.

linux lvm raid software-raid

6 Answers

  1. Best Answer

    Your current setup is like this: 

    | / | /var | /usr | /home  |
 --------------------------
|       LVM Volume         |
 --------------------------
|       RAID Volume        |
 --------------------------
| Disk 1 | Disk 2 | Disk 3 |

    It's a much simpler setup with more flexibility. You can use all of the disks in the RAID volume and slice and dice them whatever way you like with LVM. The other way isn't even worth thinking about - it's ridiculously complicated and you lose the benefits of LVM at the filesystem level.

    If you tried to RAID LVM volumes, you would be left with a normal device without any of the LVM volume benefits (e.g. growing filesystems etc.)

    • 60

  2. This is an old question, technology has advanced and the recommended setup is to use built-in RAID support of LVM (see here for setup https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Logical_Volume_Manager_Administration/raid_volumes.html ), especially if you are using SSD. Red Hat does not recommend the use of RAID 1/5/6/10 with SSD since mdadm will write the complete partition to ensure proper functioning of checksums. This can lead to faster degradation of the SSD, as stated here https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html-single/Storage_Administration_Guide/index.html#ssddeploy

    • 10

  3. Your current setup is fine. This is the recommended way to do it.

    Raid deals with keeping the bits secure/redundant/fast/whatever and LVM helps you present them in a esasy to use way.

    • 4

  4. have hardware raid and you can have lvm on top - best combination.

    • 2

  5. I am assuming you mean Hardware RAID with LVM on Top, vs. LVM and Software RAID on top of LVM. If so, I always advise to opt for hardware based RAID first. Software RAID is just that, while overhead is small, hardware RAID performance will be better 9 out of 10 times. Of course, the methodology will very much depend on your final goal. What are you trying to achieve (performance, protection, etc., etc.)

    • 0

  6. I think it makes sens to use RAID over LVM if you want to split your disks between a RAID 0 volume and a RAID 1 volume.

    With this you can't realocate space between RAID0 and RAID1

    | / | /var | /usr | /home  |
 --------------------------
|       LVM Volume 2       |
 --------------------------
|    RAID 0   |   Raid 1   |
 --------------------------
| Disk 1 | Disk 2 | Disk 3 |

    With this you can

    | / | /var | /usr | /home  |
 --------------------------
|       LVM Volume 2       |
 --------------------------
|    RAID 0   |   Raid 1   |
 --------------------------
|       LVM Volume 1       |
 --------------------------
| Disk 1 | Disk 2 | Disk 3 |

    the good thing is that you can also still move the LVM Volume 2 logical volumes between raid 0 et and raid 1 volume, by using pvmove command

    the bad thing is that the setup is complex It would be better if LVM had a better integration of software raid features.

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