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suggestion on vg

Madanagopalan S
Frequent Advisor

suggestion on vg

I need to create a vg on n class server. vg contains 4 hard disks (disk
enclosure).

Requirement :
consists 4 hard disks with mirror and striping.

How can I do it? This is for the oracle database. I require your suggestion
on parameters (disk block size, like) for the better performance. Can
some one give me the steps to create this.
Thanks.
let Start to create peaceful and happy world
3 REPLIES
Rainer_1
Honored Contributor

Re: suggestion on vg

Create pys. volume with pvcreate /dev/rdsk/c#t#d0
Create vg with your 4 disks
mkdir /dev/vgXX
mknod /dev/vgXX/group c 64 0xXX0000
vgcreate vgXX /dev/dsk/cXt#d0 /dev/dsk/cXt#d0 /dev/dsk/cYt#d0 /dev/dsk/cYt#do
Then create a phys. vol group /etc/lvmpvg
VG /dev/vgXX
PVG PV0
/dev/dsk/cXt#d0
/dev/dsk/cXt#d0
PVG PV1
/dev/dsk/cYt#d0
/dev/dsk/cYt#d0

Then lvcreate -L -D y -s -g -m 1 vgXX

Make filesystem with newfs -F vxfs -b 8192 /dev/vgXX/lvol1
(-b 8192 defines the blocksize, should be the same as your database blocksize)
Devbinder Singh Marway
Valued Contributor

Re: suggestion on vg

Rainers method is good for striping and mirroring ,
Another thing to check is how the logical volume is layed out, basically you are doing extent based striping and mirroring , so when you look at you logical volume to should show something like this
e.g. say you have 2 PVGs with 2 disks in them
PVG2 is for mirroring
PVG 1 = c0t4d0 and c0t3d0
PVG 2 = c1t3d0 and c1t4d0

your lvdisplay should show
one extent on c0t4d0 then c1t3d0(mirror)
then c0t3d0 then c1t4d0 (mirror)
and then c0t4d0 c1t3d0
c0t3d0 then c1t4d0

etc.. so this shows extent based , if your lvdisplay shows all logicalv volume on c0t4d0 and then a bit on c0t4d0 , then you have created it wrong , or you need an LVM patch .


HTH and doesn;t confuse the matter.
Seek and you shall find
Dave Wherry
Esteemed Contributor

Re: suggestion on vg

Both the previous posts are right on the money. I just wanted to ask what kind of disks you are using?
If you are using some type of array you may not need to mirror. Mirroring typically protects you from a hardware failure.
Most arrays are using some sort of Raid, 1 or 5 which protects you in the event of disk failures. If you mirror to an array you are forcing an extra write to the mirror, putting more load on the host.
It could help your read performance as the read request is serviced from the disk that has fewer requests queued to it.
If you are not using an array go with the mirror and protect yourself.