lvcreate -D versus lvcreate -i -I

[Hamid Touhouche]

Can anybody please clarify me on the difference between lvcreate -D for pe distribution over multiple disks and lvcreate using the striping option -i & -I.
Basically I have 4 disks ( each two disk connected to a different controller.)In order to achieve the optimum performance I want the logical volume to spannin equally over the 4 disks. What is the best way to do this.

Thanks for you valuable help.

[Stefan Farrelly · Accepted solution]

the -D (distributed) option is really for those who want to stripe and mirror, whereas the -i -I options are for striping only. Thats the only real difference.

[Santosh Nair_1]

Hi,

From what I could gather, the -D option is what HP calls extent based striping and has the ability to be mirrored at a later time if required (i.e. mirrored stripes). The -i & -I option specifies block striping and with it, you can set the stripe size, i.e. striping not based on extent size.

Found the following hit at dutchworks:

http://www.dutchworks.nl/htbin/hpsysadmin?h=3&dn=73976&q=lvcreate%20-D%20-i&fh

Hope this helps.

-Santosh

[Carlos Fernandez Riera]

If you choose -i -I you cannot make mirror with LVM.

-i -I let you choose size of strip and number of disk to sptrip across.

-D set 4MB ( default) strip size.

[Soren Morton]

-i and -I provide striping at the block level where -D provides distribution across mutiple disks at the extent level.

The best performing option will probably depend on if you are doing large contiguous reads and writes or small random reads and writes.

Does anyone know if a write of 20mb on a distributed volume would write to 5 disks simultaneously like striping (few i/o requests) or would it be further broken up causing more i/o requests?