Now I only have 2 disks in my server i.e. /dev/sda and /dev/sdb
Q1. Why does Linux create dm-0,dm-1 and dm-2 as separate devices ( albeit I guess these are virtual devices via Device Manager ?
As far as I can tell these are the Oracle Linux Home, the Swap Device and
the Oracle Linux Root - however Idon't see a command directly linking dm-0, and dm-1 which the /home and / mount points
Q2. How do you tell if the dm-0, dm-1 and dm-2 are using the sda or sdb device ?
Q3. I see dm-0 ( Linux Home ) is experiencing a high rate of tps ( transactions per second ? ) whereas the sda device ( which I believe dm-0 is ultamately on ) is experiencing a high amount of data read - is this where my performance problem resides ?
Q4. Is there a way to tell which mounted file system is performing poorly ?
Q5. Why when I increase the Swap from 3 Gb to 19 Gb, I do this by adding a swap file ? Why is the 3 Gb shown as a swap device but the additional 16 Gb is not shown as a device ?
Code:
lab3:/root>swapon
NAME TYPE SIZE USED PRIO
/swapfile1 file 16G 6.8G -1
/dev/dm-1 partition 3G 0B -2
any help greatly appreciated
Jim
Last edited by Scrutinizer; 12-01-2015 at 12:18 PM..
Reason: Code tags
Check out the output of (output here is from one of my machines)..
Code:
ls -lart /dev/dm*
brw-rw----. 1 root disk253, 1 Nov 25 10:06 /dev/dm-1
brw-rw----. 1 root disk 253, 0 Nov 25 10:06 /dev/dm-0
brw-rw----. 1 root disk 253, 4 Nov 25 10:06 /dev/dm-4
brw-rw----. 1 root disk 253, 3 Nov 25 10:06 /dev/dm-3
brw-rw----. 1 root disk 253, 2 Nov 25 10:06 /dev/dm-2
Notice the MAJOR,MINOR numbers above
Code:
# dmsetup info
Name: rootvg-tmp
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 1
Event number: 0
Major, minor: 253, 4
Number of targets: 1
..... # other output.
So rootvg-tmp coresponds with /dev/dm-4 device.
vgdisplay -v will provide output which physical volumes belong to which volume group.
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