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storage disk details

 
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Operating Systems Linux Red Hat storage disk details
# 1  
storage disk details

Hi,

We have a OEL5.7 installed and which has a storage attached on it.
While running application it shows poor performance for Disk IO "dm-0"

Now the question is how do I find what exactly is "dm-0"

Code:
[root@~]# iostat
Linux 2.6.32-100.23.1.el5    03/10/2012

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           1.46    0.00    1.20    4.52    0.00   92.82

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
sda              12.49        87.93       143.30   75059335  122323742
sda1              0.00         0.03         0.00      21774         30
sda2             12.49        87.90       143.30   75036897  122323712
dm-0              1.34         5.43         8.85    4636962    7556976
dm-1             27.11        82.47       134.44   70399536  114766736


[root@~]# fdisk -l

Disk /dev/sda: 30.9 GB, 30999052288 bytes
255 heads, 63 sectors/track, 3768 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      104391   83  Linux
/dev/sda2              14        3768    30162037+  8e  Linux LVM

[root@~]# cat /proc/partitions
major minor  #blocks  name

   8        0   30272512 sda
   8        1     104391 sda1
   8        2   30162037 sda2
 253        0   15269888 dm-0
 253        1   14876672 dm-1

Here are few commands I tried, but not able to know what exactly (mount point) dm-0 and dm-1 are referring to..

Please suggest...

Last edited by DukeNuke2; 03-09-2012 at 02:55 AM..
# 2  
have a look here:
DM Multipath
# 3  
Thanks DukeNuke2...

I just tried to search path to LUN's for current env.. got following output..

Code:
[root@ mapper]# multipath -l
Mar 10 03:14:48 | /etc/multipath.conf does not exist, blacklisting all devices.
Mar 10 03:14:48 | A sample multipath.conf file is located at
Mar 10 03:14:48 | /usr/share/doc/device-mapper-multipath-0.4.9/multipath.conf
Mar 10 03:14:48 | You can run /sbin/mpathconf to create or modify /etc/multipath.conf
Mar 10 03:14:48 | DM multipath kernel driver not loaded


I am actually new to this, can you please guide where exactly i need to search in system..

Warm regards!

Last edited by DukeNuke2; 03-09-2012 at 09:24 AM..
# 4  
dm-x is pretty much anything done through the device mapper. In your case I'm guessing it's one of the LVs. Do a ls -l /dev/mapper and look for the LV with the appropriate major and minor number.
# 5  
Thanks for the reply...

Here I can see is..
Code:
[root@ mapper]# ls -l /dev/mapper
total 0
crw------- 1 root root  10, 62 Feb 29 05:23 control
brw-rw---- 1 root disk 253,  0 Feb 29 05:23 VolGroup00-LogVol00
brw-rw---- 1 root disk 253,  1 Feb 29 05:23 VolGroup00-LogVol01

But, what I want to know is which storage actually dm-0 and dm-1 refer too...

Please help...
# 6  
Oh, that's easy. dm-0 corresponds to the logical volume VolGroup00-LogVol00. Since you have only one disk, and only one VG, it's the internal disk.
This User Gave Thanks to pludi For This Post:
# 7  
Thanks pludi,

So you mean dm-0 and dm-1 here are my hdd?
Also, where can i see the details of storage disk's then? we have configured it on our system..

Regards!

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