Red Hat

Code:

cmdline #  lvdisplay|awk  '/LV Name/{n=$3} /Block device/{d=$3; sub(".*:","dm-",d); print d,n;}'

What they're keying off of is the minor number on the block device. A major number of 253 means it's a devicemapper device while the minor number is used in the dm-X naming scheme. Your "ls -l" shows the minor number of "0" (i.e "dm-0") is associated with VolGroup00-LogVol00. So the long and the short of it is that dm-0 is another name for the VolGroup00-LogVol00 logical volume.

Judging from your initial output it looks like sda is a local drive and I don't see anything to imply that VolGroup00 has anything but local volumes in it (you can check with "pvs" though. If sda is the only thing that shows up then you're good).

What specific details were you hoping to get at?

The easiest way to get a clear picture of your storage layout would be to run:

Code:

pvs
vgs
lvs
mount
cat /proc/swaps

Could you please post the output of these commands?

/dev/sda is certainly the internal drive and by default /dev/sda1 is /boot and /dev/sda2 is a physical volume with the volume group VolGroup00 which contains the logical volumes LogVol00 and LogVol01. LogVol00 shows up as /dev/dm-0 and is typically used for the root filesystem (/) and LogVol01 is /dev/dm-1 and is typically used as swap. But the above commands will confirm this.

There doesn't appear to be any external storage in use on this system.

As to your performance problem, if the configuration assumptions above are correct, then you have minimal I/O activity to the root filesystem, but a ton of activity to dm-1, the swap partition.

Simply put, when Linux starts to run out of free memory it moves pages to and from disk space in the swap partition. If the system is actively paging, performance will be awful. (Memory access is about a million times faster than disk access).

Running:

Code:

free -m
sar -B
vmstat

will give you a quick view of your memory and swap usage. Please post the output of that, too.

Based on the limited information presented I'd bet your problem is that the system doesn't have enough RAM to properly support the application and the system is actively paging to/from swap. Under those circumstances, performance will be lousy. Some static use of swap space is OK, but active paging activity is to be avoided at all costs.