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redhatalignment [2013/04/20 13:21] (current)
sjoerd created
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 += Red Hat LUN Alignment =
 +
 +Red Hat Enterprise Linux 6 should align it's disk correctly to the underlying LUNs but to make sure you should always check:
 +
 +First, check which partitions are seen by the kernel:
 +<​code>​
 +[root@redhatbox ~]# cat /​proc/​partitions
 +major minor  #​blocks ​ name
 +
 +   ​8 ​       0   ​20971520 sda
 +   ​8 ​       1     ​204800 sda1
 +   ​8 ​       2   ​20765696 sda2
 + ​253 ​       0    2097152 dm-0
 + ​253 ​       1    5242880 dm-1
 + ​253 ​       2    5242880 dm-2
 + ​253 ​       3    5242880 dm-3
 + ​253 ​       4    2097152 dm-4
 +</​code>​
 +
 +Then, check whether the partitions are aligned or not:
 +<​code>​
 +[root@redhatbox ~]# fdisk -lu /dev/sda
 +
 +Disk /dev/sda: 21.5 GB, 21474836480 bytes
 +64 heads, 32 sectors/​track,​ 20480 cylinders, total 41943040 sectors
 +Units = sectors of 1 * 512 = 512 bytes
 +Sector size (logical/​physical):​ 512 bytes / 512 bytes
 +I/O size (minimum/​optimal):​ 512 bytes / 512 bytes
 +Disk identifier: 0x000c0750
 +
 +   ​Device Boot      Start         ​End ​     Blocks ​  ​Id ​ System
 +/​dev/​sda1 ​  ​* ​       2048      411647 ​     204800 ​  ​83 ​ Linux
 +Partition 1 does not end on cylinder boundary.
 +/​dev/​sda2 ​         411648 ​   41943039 ​   20765696 ​  ​8e ​ Linux LVM
 +Partition 2 does not end on cylinder boundary.
 +</​code>​
 +The start sector should be cleanly divisible by 8, if so they are aligned. This counts for all partitions, not just the first one. Both starting sectors are, do the VM is aligned. ​
 +
 +{{tag>​linux storage performance}}
  
redhatalignment.txt ยท Last modified: 2013/04/20 13:21 by sjoerd