On 19/09/2009, at 6:28 PM, Fabian Arrotin wrote:
Oliver Ransom wrote:
Hi everyone.
This isn't specifically a CentOS question, since it could apply for any distro but I hope someone can answer it anyway.
I took the following steps but was puzzled by the outcome of the test at the end:
- Create a RAID1 array called md3 with two 750GB drives
- Create a RAID1 array called md9 with two 500GB drives
- Initialise md3 then md9 as physical volumes (pvcreate)
- Create a new volume group called "3ware" with md3 (helps me
remember what controller the disks are on) 5. Use vgextend and add md9 to the 3ware volume group. 6. Add a logical volume filling the volume group then create a ext3 filesystem on the entire volume.
Now I started moving a lot of data onto the volume and iostat said all the data was being written to md9. Why that array? How does it decide which physical volume to write to?
I could not find any documentation or information online about how exactly this works.
What ? no documentation covering LVM admin on/for CentOS ? hmm, is http://www.centos.org/docs/5/html/5.2/Cluster_Logical_Volume_Manager/ not reachable from your side ? How have you configured you LV ? linear or stripped ?
Hi,
I did not say I could not find any documentation covering LVM admin for CentOS. I said I could not find any documentation explaining exactly how, in the context of my message, the "decision" was made.
I used the default configuration examples from the LVM HOWTO which results in a linear arrangement. My question would not have come up if I had set things up in a striped arrangement.
The link below says "The physical storage is concatenated". http://www.centos.org/docs/5/html/5.2/Cluster_Logical_Volume_Manager/linear_...
That doesn't really answer the question from my example though, if it was concatenated and I added md3 before md9, shouldn't it have been writing to md3 first? That's what I would have expected.
Oliver
--
Fabian Arrotin idea=`grep -i clue /dev/brain` test -z "$idea" && echo "sorry, init 6 in progress" || sh ./answer.sh
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