Re: slow lvm

I hate those. They should just have made it report it's real sector size 
and wait for controllers and drivers to support it.

Now, you have to make your partitions to start at megabyte boundaries to 
get full speed, so that the sectors oft the file system come to lie on 
the physical sectors, or else it will need read out every sector before 
writing to it.

Am 11.08.2011 12:50, schrieb Matus UHLAR - fantomas:
>> On Thursday 11 August 2011 07:48:45 Keith Edmunds wrote:
>>> Do the disks have 1K sectors or 4K sectors?
>
> On 11.08.11 11:37, mimo wrote:
>> fdisk -l /dev/sdd
> hmmm, since when does fdisk show that?
>
>
>> Disk /dev/sdd: 2000.4 GB, 2000398934016 bytes
>
> It's 2T, it should be 4k/sec
>
>> Sector size (logical/physical): 512 bytes / 4096 bytes
>
> See? It is...
>
>> I/O size (minimum/optimal): 4096 bytes / 4096 bytes
>
> that's why partisions should be rounded on 4K limit.
>
>> Device Boot Start End Blocks Id System
>> /dev/sdd1 * 1 1216 9764864 fd Linux raid autodetect
>> /dev/sdd2 1216 2432 9765888 fd Linux raid autodetect
>> /dev/sdd3 2432 8511 48828416 fd Linux raid autodetect
>> /dev/sdd4 8511 243201 1885151840+ fd Linux raid autodetect
>
> the 'fdisk -lu /dev/sdd' will tell you boundaris on sector range.
>
>> fdisk -l /dev/sda
>>
>> Disk /dev/sda: 2000.4 GB, 2000398934016 bytes
>> 255 heads, 63 sectors/track, 243201 cylinders
>> Units = cylinders of 16065 * 512 = 8225280 bytes
>> Sector size (logical/physical): 512 bytes / 512 bytes
>> I/O size (minimum/optimal): 512 bytes / 512 bytes
>
> This disk tells it has 512B sectors, but that may be just configuration
> and reality might be different.
> Therefore you could try with 4K rounding too.
>
>> Disk identifier: 0x000e0666
>>
>> Device Boot Start End Blocks Id System
>> /dev/sda1 * 1 1216 9764864 fd Linux raid autodetect
>> /dev/sda2 1216 2432 9765888 fd Linux raid autodetect
>> /dev/sda3 2432 8511 48828416 fd Linux raid autodetect
>> /dev/sda4 8511 243201 1885151840+ fd Linux raid autodetect
>