[linux-lvm] raid0 - no performance increase??

[linux-lvm] raid0 - no performance increase??

[lejeczek]

Hi guys,

I have a simple raid0 lvm comprising of two NVME devices.
I'd expect performance of such a volume to be higher than a
"regular" volume ran of a single NVME, but simple dbench
shows such raid0 volume to the same "slow" as a single NVME
volume.
The system is a Centos 8 with 5.8.14-1.el8.elrepo.x86_64 and
default kernels.

raid0:
  #Str #DStr Stripe Type   Devices                   
     2     2 64.00k raid0  0_rimage_0(0),0_rimage_1(0)
     1     1     0  linear /dev/nvme0n1(0)           
     1     1     0  linear /dev/nvme1n1(0)

Care to share your thoughts? I'll be grateful.
many thanks, L

Re: [linux-lvm] raid0 - no performance increase??

[Bastian Blank]

On Sat, Oct 10, 2020 at 05:52:32PM +0100, lejeczek wrote:
> I have a simple raid0 lvm comprising of two NVME devices.
> I'd expect performance of such a volume to be higher than a
> "regular" volume ran of a single NVME, but simple dbench
> shows such raid0 volume to the same "slow" as a single NVME
> volume.

Why do you think?  What is dbench anyway?  Linear access is not going to
be faster, as it is dominated by latency.  Please use fio with _random_
reads or writes and a useful queue depth.

Also, what do you mean with slow?  500k IOPS?

Bastian

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