Re: slow lvm

[mimo <mimo@restoel.net>]

On Thursday 11 August 2011 12:52:36 Bachsau WebWorX wrote:
> 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.

Thanks for everyone's help. I found something about these "Green" drives going to park every 8 secs so I used 

hdparm -S 242 /dev/sdd

to change the standby. That brought a tiny improvement. So the next step I deleted the whole lvm and used some other advice by running 

cfdisk -h 224 -s 56 /dev/sdd

Which gives a partition table that isn't at all divisible by 8 or start on 2048 but performance had improved quite dramatically. Originally I got 71MB/s when writing one large 20GB file. Writing to a raw partition I now get 117MB/s (also with lvm). Is that what I should be achieving?

I just wonder whether I've got it right now as the partition table looks plain weird..

fdisk -lu /dev/sdd

Disk /dev/sdd: 2000.4 GB, 2000398934016 bytes
224 heads, 56 sectors/track, 311465 cylinders, total 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x0005f6d7

   Device Boot      Start         End      Blocks   Id  System
/dev/sdd1   *          56    19531007     9765476   fd  Linux raid autodetect
/dev/sdd2        19531008    39062015     9765504   fd  Linux raid autodetect
/dev/sdd3        39062016   136717055    48827520   fd  Linux raid autodetect
/dev/sdd4       136717056  3907016959  1885149952   fd  Linux raid autodetect


mimo