[CentOS] Centos 5 on Large Disks

Anup Shukla anup at iamcool.net
Wed Oct 24 10:12:03 UTC 2007

Morten Torstensen wrote:
> Anup Shukla wrote:
>> Still, given the suggestion, i will surely try to reduce the number of 
>> slices.
> I would make one system LUN at say 20GB and one data LUN with the rest 
> of the RADI5 space.
> On the system LUN I would make a /boot filesystem and a LVM partition 
> with at least a / filesystem and swap. Usually I make /, /usr, /opt, 
> /home, /var and /tmp but it varies a bit depending on what kind of 
> machine it is.
> The data LUN I would use as a PV directly for LVM and not bother with 
> partitions at all.

I created 500G slices. Partitioned and mounted them
Then did a simple
"time dd if=/dev/zero of=/mnt/data1 bs=1k count=1200000"
This gave me a speed of over 150MB/s

Then i deleted entire RAID thing.. recreate 2 LUNs
30G, and whatever is left.

Create a PV on the bigger drive with 1 VG and 3 LVs of equal sizes.

Format and run the dd command again.
The speed is 130MB/s now.

Its a bit confusing.
Does LVM slow down things? Or i did something that is not really of any 
relevance to check IO speed.

I used mkfs.ext3 -m0 -E stride=96 -O dir_index /dev/sdb1 ...
I have a RAID5 volume consisting of 6 disk with stripe size = 64k
I hope the stride=96 is optimal.

Should i stick with LVM, or go back to the older way?

Thank you.


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