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Queue depth during a vmware migrate

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Frequent Advisor

Queue depth during a vmware migrate



Not sure if anyone can tell me if this is something I need to fix on the san or on my esx hosts.  When we want to migrate a guest vm onto the san the initial start of the migrate causeses really high QDT on the san.  When I start migrating the vm it starts off really slow, stalling at a small percent, say 3% or 6%, and the QDT stays really high for a while, then after 10 minutes or so the QDT drops down to normal levels and the migration continues and all is fine.


This is on a 2 node p4500 g2.  The normal QDT we have is anywhere betwen 2 and 10, but when I try migrating the vm it goes up to 148!


Esx version 4.x and saniq version 9.0




Gediminas Vilutis
Frequent Advisor

Re: Queue depth during a vmware migrate

What is background total load (from all machines, VMs, etc) in IOPS on cluster? Disks are 7.2 or 15 krpm?



Frequent Advisor

Re: Queue depth during a vmware migrate

Current normal usage:


200-400  IOPS on 15K 600GB SAS drives.


When I start a migrate to the san it jumps to 14000 IOPS and a Queue Depth of about 120 and sometimes drops to 2.


Honored Contributor

Re: Queue depth during a vmware migrate

You may want to check several things -

1. Are the hosts created on LHN with Load Balancing enabled? If not, enable it.

2. Where are all the iSCSI sessions are running? Are they load balance between 2 nodes? You can check this by clicking on the Cluster and right hand side pane should have iSCSI session tab.

3. If using Active/Passive NIC bonding, are the active NICs on the same switch? It's preferred to have them on the same switch so that volume mirroring doesn't lag by going across the ISL between the switches. (Assuming you have 2 switches ISL).

4. Do you have Flow-Control enabled on all the ports (ESX and Lefthand NICs)?

5. Make sure you don't have jumbo frames enabled for partial setup. Either it has to be completely switched off or should be enabled for ESX, Network switches and Lefthand. (Check the ESX vmnic frame size using esxcfg-vswitch -l command.)

6. On both Lefthand nodes run the diagnostic test, all should pass specially the BBU. that might impact the performance big time.


Apart from this, you may try -

1. Use vMotion on a different datastore volume, which has different block size (1MB, 2MB, 4MB & 8MB block sizes are available for ESX4.x datastores for different VMDK sizes allowed). See if that makes difference.

2. Upgrade to SANiQ9.5, I have personally seen performance improvements (not very drastic though) with SANiQ9.5 so it will be worth giving a shot.

3. Reset the counter on network ports for lefthand before starting vMotion and check it after that, sometimes NIC port errors might be causing slow performance due to errors which mirroring the data across. (not a very likely cause but doesn't hurt checking it).


Please let us know the results.

Frequent Advisor

Re: Queue depth during a vmware migrate

1. Yes

2. Yes the are balanced.

3. Not using active/passive

4. No it looks like not on the switchports connected to the esx hosts.

5. Don't use jumbo frames.

6. Will have to try that.


Looks like I will have to enable flow control.


Thanks for the detailed post.

Regular Advisor

Re: Queue depth during a vmware migrate

Sometimes I really think HP should include a manual in the box with FAQ for these units...


Flow control makes such a huge difference to the performance of them for whatever reason - and it is not clearly documented (in BOLD )and no one normally reads the manuals anyway :)


David Tocker