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[linux-lvm] Sanity check: newbie wants strange LVM configuration



I've got two disk drives, 12 & 16 GB IDE. I'm adding a third 40GB drive. Time to start using LVM...

I want to get better performance, so, I'll put the 40GB drive on one IDE controller, the other two drives on the second controller. I'll make two partitions on the 40GB drive that match the disk sizes of the existing drives, and stripe each with it's match on the 40GB drive, creating two raid0 arrays (one 12+12, and the other 16+16). By placing the dual-partitioned 40GB drive stand-alone on one IDE controller, each striped with a partition/drive on the other controller, any given file will only be striped across one partition on each controller, so I should see the performance benefit of striping (on IDE).

Should I use LVM or MD to do the striping (they both can do it, I was just wondering which would be a better choice)?

Even if I use MD to stripe, I'd use LVM to append the two drives together.

Before appending the drives, I'd make a temporary partition on the 40GB drive, and copy the current contents of the 16GB (/home) drive to the temporary partition. Then, I'd make the 16+16 raid0 a logical volume, create a reiserfs on it, and copy the information back from the temporary partition, to the new reiserfs.

Since the 12GB drive is the current root partition, it's a bit trickier to copy. I'd copy it's contents to a temporary partition on the 40GB drive, boot from that temporary partition, then create the second 12+12 raid0, and add it to the first logical volume, then expand the reiserfs to cover both, copy the root file system from the temporary partition to the new logical volume, and setup a reiserfs root and boot.

Is this the correct approach for upgrading?

Finally, I'll have ~10GB unallocated on the 40GB drive. I was thinking of adding this to the end of the current logical volume (and, again, expand the reiserfs to cover the additional space).

Since any file system looses performance when more than 90% full, this final non-striped partition would be in a position where performance would degrade anyway, and keep the raid0's in a position for full performance.

Is that correct?

Sort of off-topic (not LVM related)...

I've got an IDE CDROM drive that I want to put on the same controller as the 40GB drive. I've been told that new UDMA drives do not have the PIO performance hit associated with CDROM drives, so I should be able to get full performance from my 40GB drive, even with a CDROM on the same IDE controller.

Is that correct (or should I junk the IDE CDROM)?

Thanks,

Chris



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