Opinions on large luns

[Mark Killen]

We are implementating a L2000 connected to an oem disk san.(Compaq). We are building a raid set of 4X36gb drives giving us 100gb usable and it will look like one 100gb lun. I have done some testing but was not able to do real world testing, so my questions are What are some of the repercussions of using a large lun? and Will monitoring tools cause system slowdowns rechecking the lun as it should show close to 100% usage all the time.
Thanks
Mark

[A. Clay Stephenson · Accepted solution]

Hi Mark,

I'm not familiar with Compaq arrays but I can make some general comments. First, to the UNIX box this will appear as one big device so yes
to glance, measureware, etc. it will APPEAR that the disk is saturated. The performance tools don't do a very good job of measuring arrays. They can't; they think it's one disk.
If the Compaq array has multiple dual (or multiple active channels) then there is something you can do.
Rather then 1 100GB LUN make it 2 50GB LUN's.
Then configure your volume group as these two LUNS with LUN1's primary path different from LUN2's. This will divide the I/O over two channels and the performance tools will be happier and the performance will improve.