Bug#513924: lvmcfg: Physical Extent (PE) size too small
On 02/02/09 17:50, Ferenc Wagner wrote:
> Laurent Grawet <debian-bugs@grawet.be> writes:
>
>> The default PE size is too small (4MB) for some use when creating
>> volume groups (VG) with debian-installer.
>>
>> If you're dealing with large amounts of data, it is highly
>> suggested to go for a larger extent size for performance reasons.
>
> man vgcreate says:
>
> If the volume group metadata uses lvm2 format those restrictions do
> not apply, but having a large number of extents will slow down the
> tools but have no impact on I/O performance to the logical volume.
>
> Thus I don't find it 'highly suggested'. What do you base your
> statement on?
I read it here and there some time ago and took it as best practice.
For example :
"Reducing the physical extent size increases the size of the LVM data
structures but gives a finer granularity for assigning storage to
logical volumes. Increasing the physical extent size slightly reduces
the LVM overhead, increasing performance."
http://codeidol.com/unix/fedora/Advanced-Installation/Configuring-RAID-and-LVM-During-Installation/
The man page seems to prove I was wrong.
Maybe it applied only to LVM1 (like small PE limit per VG).
I'm still wondering why Red Hat set it to 32 MB by default.
Laurent
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