disk i/o slow on iscsi+lvm

nikybiasion

Member
May 28, 2012
12
1
23
Hello, i've an hp p2000 iscsi/fc combo connected with iscsi with an hp dl180 with two dedicated nics. The san has 8 disks in raid 50.
I've configured the san with two different subnets for multipath.

I've created a guest with Windows 2008 R2 on an LVM disk using virtio driver. I've tried to copy a 4GB file and trasfer speed is only 45MB/s, i've created a logical volume formatted in ext3 and i've tried the same operation, transfer speed is 100MB/s.

Multipath seems working, network traffic to the san is distribuited on both nics, but may be that multipath/iscsi is not tuned very well.

Someone has a similar configuration? 45Mb/s is too slow?
 

lnxusr

Guest
I have a setup with 2 Dell Equallogic SAN units. I have 4 ethernet ports connecting each of the 3 Proxmox 2.0 units to the SAN network. The SAN network is provided by a Cisco 3750 stack of 2 units.

I get a performance of 250+mb/s for copy actions from d:\ to d:\ on a Windows 2008 R2 vm.

I don't know the expected performance would be for your hp unit. What is you expectation, regardless of using Proxmox?

My clients setup:

Code:
        -------------------------------------
        |        LVM Volumes	            |
        -------------------------------------
      /		  |		  |	      \
     /		  |		  |	       \
    /		  |		  |		\
   /		  |		  |		 \
path0		path1		path2		path3
  |		  |		  |		  |
  |		  |		  |		  |
  |		  |		  |		  |
  |		  |		  |		  |
vmbr100		vmbr101		vmbr102		vmbr103
  |		  |		  |		  |
  |		  |		  |		  |
  |		  |		  |		  |
  |		  |		  |		  |
eth4		eth5		eth8		eth9
  |		  |		  |		  |
  |		  |		  |		  |
  |		  |		  |		  |
  |		  |		  |		  |
sansw-1		sansw-2		sansw-1		sansw-2
  \               |               |               /
   \              |               |              /
    \             |               |             /
     \            |               |            /
      \           |               |           /
       \          |               |          /
        -------------------------------------
        |        Dell Equallogic SAN        |
        -------------------------------------
 

nikybiasion

Member
May 28, 2012
12
1
23
I expected better performance for my iscsi san, but i think that 50mb/s is the raid speed for a read/write operation.
If i copy a file from my linux node to a virtual machine, the transfer rate is 75 mb/s. I suppose that this speed is a limit for a raid 50 with 8 sas disks.
I don't know if a better driver can improve performance (i use virtio), i've also tried ide mode, performance is even worse, only 18mb/s.
 

lnxusr

Guest
I use virtio disks in my vm's. Can you see multiple connection on your SAN? That's how I check if mpio is actually working properly on our Dell Equallogic. Also make sure the mpio paths are discrete and use different physical ethernet ports. Otherwise mpio has a negative impact on performance.
 

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