[linux-lvm] linux-lvm Digest, Vol 190, Issue 6

[Daniel Janzon]

> From: Marian Csontos <mcsontos at redhat.com>

>> The origin of my problem is indeed the poor performance of RAID5,
>> which maxes out the single core the driver runs on. But if I accept that
>> as a given, the next problem is LVM striping. Since I do get 10x better

>What stripesize was used for striped LV? IIRC the default is 64k.

I ran  "lvcreate -L 2400G -i8 -I512 -n volume-name group-name".  And I tried various numbers, 512 was the greatest I could set but does not seem to be crucial for performance.

> IIUC you are serving mostly large files. I have no numbers, and no HW to
> test the hypothesis, but using larger stripesize could help here as this
> would split the load on multiple RAID5 volumes, while not splitting the
> IOs too early into too many small requests.

File size are typically a few megabytes. I guess the file abstraction is not visible
on the LVM layer though, but at least there won't be many blocks with a lot
of unused space.