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[linux-lvm] diff. in striping between HP-UX and Linux LVM



Hi all,

I have to work with both systems an found some differences in the striping between the two kinds of LVM. I created a vg consisting of two disks on the HP-UX and on the linux system and a lv with the "-i 2 -I 64"-option.

In the case of HP-UX the first LE points to the first PE on the first disk, the second LE points to the first PE of the second disk and so on. 

In case of Linux LVM the LEs corrospond to the PEs, there is no alternation and therefore no enhancement of performance because only one disk will be used at the same time.

Where I am wrong?

ciao
Stephan

HP-UX:
--- Logical volumes ---
LV Name                     /dev/vgmail/lvol1
VG Name                     /dev/vgmail
LV Permission               read/write
LV Status                   available/syncd
Mirror copies               0
Consistency Recovery        MWC
Schedule                    striped
LV Size (Mbytes)            4096
Current LE                  1024
Allocated PE                1024
Stripes                     2
Stripe Size (Kbytes)        64
Bad block                   NONE
Allocation                  strict
IO Timeout (Seconds)        default

   --- Distribution of logical volume ---
   PV Name            LE on PV  PE on PV
   /dev/dsk/c4t6d1    512       512
   /dev/dsk/c6t6d2    512       512

   --- Logical extents ---
   LE    PV1                PE1   Status 1
   00000 /dev/dsk/c4t6d1    00000 current
   00001 /dev/dsk/c6t6d2    00000 current
   00002 /dev/dsk/c4t6d1    00001 current
   00003 /dev/dsk/c6t6d2    00001 current
   00004 /dev/dsk/c4t6d1    00002 current
   00005 /dev/dsk/c6t6d2    00002 current
   00006 /dev/dsk/c4t6d1    00003 current
   00007 /dev/dsk/c6t6d2    00003 current
  ...

Linux:
--- Logical volume ---
LV Name                /dev/vg00/lvol1
VG Name                vg00
LV Write Access        read/write
LV Status              available
LV #                   1
# open                 1
LV Size                4 GB
Current LE             1024
Allocated LE           1024
Stripes                2
Stripe size (KByte)    64
Allocation             next free
Read ahead sectors     120
Block device           58:0

   --- Distribution of logical volume on 2 physical volumes  ---
   PV Name                  PE on PV     reads      writes
   /dev/sdb1                512          1536487    1472056
   /dev/sdc1                512          1535960    1472315

   --- logical volume i/o statistic ---
   3072447 reads  2944371 writes

   --- Logical extents ---
   LE    PV                        PE     reads      writes
   00000 /dev/sdb1                 00000  0          1008
   00001 /dev/sdb1                 00001  0          1024
   00002 /dev/sdb1                 00002  0          590
   00003 /dev/sdb1                 00003  0          848
   00004 /dev/sdb1                 00004  0          16
   00005 /dev/sdb1                 00005  0          0
   00006 /dev/sdb1                 00006  272        2594
 


--
LDS Brandenburg
Dr. Stephan Hendl
fon: +49-(0)331-39 471
fax: +49-(0)331-27548 1187
EMail: stephan hendl lds brandenburg de





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