Striping and Logical Volumes

[Rodian Paul]

Perhaps someone can explain the following to me... 

I created a logical volume consisting of 3 * 1.2GB IPI2 drives, with a 
stripe of 3.

Once the sucker's created (using partition 7 on each drive, i.e the whole
drive, all partitions the same size) I get the following output from 'df':

(all figures in 512K blocks)

Filesystem                 Type  blocks     use   avail %use  Mounted on
/dev/dsk/lv0                efs 4901760  669740 4232020  14%  /prod

Now if I take a look at a 1.2GB SMD drive (all I've got for reference but I
assume a formatted SMD is close to a formatted IPI) I get the following
amount of blocks on an efs file system: 1921920 blocks
           Mutliply that * 3 and I get: 5765760 blocks
     Subtract the difference of the lv: 4901760 blocks
                             and I get:  864000 blocks

Or approx 400MB difference. Now I assume that there are a whole lot of
tables created with a logical volume, even more if striped. I don't
recall reading anything about how much space these tables will take up
in the manuals (allthough a comment may in fact be there). So, could
someone perhaps explain to me what kind of size differences to expect with 
logical volumes and if striping uses more space.

If striping does in fact take up more space (I can't test this out at the 
moment as the machine must stay up) can I expect more throughput? The manual 
section I read said that ideally, you should arrange to connect the disks
you are striping accross to be on different controllers. We're only using 
1 (Xylogics 7800 16-drive IPI disk controller 0: Firmware version 2.2.4)
for 4 IPI2's. The machine is a 380s with 256MB RAM and doesn't have any 
other drives on it as yet.

Can I expect much of a difference in performance if I remove the stripe?

Any comments will be greatly appreciated.
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