Re: higher agcount on LVM2 thinp volumes

[Chris Murphy <lists@xxxxxxxxxxxxxxxxx>]

On Aug 29, 2013, at 9:24 PM, Chris Murphy <lists@xxxxxxxxxxxxxxxxx> wrote:

> 
> On Aug 29, 2013, at 9:19 PM, Eric Sandeen <sandeen@xxxxxxxxxxx> wrote:
>> 
>> Argh sorry, how did I type THAT?
>> 
>> # blockdev --getiomin --getioopt /dev/mapper/vg1-data
> 
> conventional LV:
> [root@f19s ~]# blockdev --getiomin --getioopt /dev/mapper/vg1-data
> 512
> 0
> 
> thinp LV:
> 
> [root@f19s ~]# blockdev --getiomin --getioopt /dev/mapper/vg1-data
> 512
> 262144


It's tied to the chunk size of the thinp. If I create a 4MB chunk size, ioopt 
goes up to match it. The default is 256KB, which reflects the values above.


[root@f19s ~]# lvcreate -L 400G --type thin-pool -c 4M --thinpool thinp vg1
  device-mapper: remove ioctl on  failed: Device or resource busy
  Logical volume "thinp" created
[root@f19s ~]# lvcreate -V 100G -T vg1/thinp --name data
  Logical volume "data" created
[root@f19s ~]# blockdev --getiomin --getioopt /dev/mapper/vg1-data
512
4194304


Chris Murphy