striping and mirroring at 11.11

[Jon Talbot]

Hi

On a HP-UX 11.11 wkstn I wish to stripe 1 lvol across 4 x 4.3GB disks and mirror to another 4 x 4.3GB disks. The lvcreate man page doesn't make it clear enough to me on whether or not I can do this. Any advice?

Gary.

[James Murtagh]

Hi Gary,

You can't use block striping if you want to mirror, i.e. using the -i option in lvrcreate/lvextend, you need to use extent based distributed logical volumes and physical volume groups. An example :

1) create your /etc/lvmpvg file to set up the physical volume groups (obviously your device files may be different) :

VG /dev/vg01
PVG PV0
/dev/dsk/c0t2d0
/dev/dsk/c0t2d1
/dev/dsk/c0t2d2
/dev/dsk/c0t2d3
PVG PV1
/dev/dsk/c1t2d0
/dev/dsk/c1t2d1
/dev/dsk/c1t2d2
/dev/dsk/c1t2d3

All devices you want to "stripe" onto will we in one PVG, the mirrors in the other.

2) Use:

# lvcreate -l 250 -D y -s g -m 1 vg01

To create a 1 GB distributed lvol with mirrors. In 10.20 or 11.00 I believe you needed a patch to run this command on one line but I believe it is built into 11i. However, this may not be suitable if you need a finer granularity in your stripe size, the default extent size in LVM is 4 MB.

Cheers,

James.

[Jon Talbot]

Thanks James, I'll give it a go.

Gary.

[Jeff Schussele]

Hi Jon,

Extent-based striping is frankly *not* the way to go. Simply for the fact that 1MB is the minimum extent size - ergo the minimum stripe size.
You should use a RAID array that gives you true HW based striping - it *always* beats SW-based striping hands-down performance-wise & then use LVM for alternate links - Mission Accomplished.

My $0.02,
Jeff

[F.V. Porcella]

I'd have to agree with Jeff.
HW striping typically beats the SW equiv.

However since this is a workstation, and I doubt you have a spare array lying around,
AND it looks like your using a Jamacia Box so... if you really need to do the striping the only realistic way is the way James suggested: mirroring striped PVG's.

However if your using a Jamacia box with F/W SCSI with 20 Mb/s BW, are you really going to get all that much for your efforts?

Phil