Yellow Bricks

by Duncan Epping

Storage

Fiber channel round-robin load balancing

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There’s a nice article about “round-robin” load balancing on SystemsArchitech which got me a bit dazzled about this new functionality:

esxcfg-mpath – lun <*.lun> —policy custom –H minq –T any –C 0 –B 2048
The policy states that the LUN should utilize a custom policy that determines which (of two) HBA to utilize based on the minimum queue length. This HBA selection is triggered every 2048 blocks transmitted to a given LUN over the same target. The policy will use any targets available to either of the two HBAs. In using storage that manages host port load-balancing, LUNs will only have two paths (one per fabric) and the storage array will perform storage array host port balancing from within its own management. With other storage arrays it is typical to perform this host port balancing from the hosts accessing the given storage array.

With 10 ESX hosts set with this policy wouldn’t it probably cause path thrashing on an active/active SAN? You never know which controller will access a specific LUN and if your unlucky it will be switching from controller A to controller B every millisecond. Anyone else any thoughts on this new feature and the possible danger?

Netapp SnapManager for Virtual Infrastructure

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Netapp just announced a new product “SnapManager® for Virtual Infrastructure”:

SnapManager for Virtual Infrastructure enables customers to protect their VMware environments with automated data protection and recovery of their virtual machines. SnapManager for Virtual Infrastructure dramatically reduces human error and increases server utilization for application workloads by eliminating the interruptions and performance impact caused by traditional server-hosted backups and restores. As a result, customers can protect their data more reliably. More information is available at www.netapp.com.

VCB: I forgot all about “automount disable” what now?

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Before installing VCB and connecting the proxy host to the SAN you should disable automount via diskpart(cmd, diskpart, automount disable, automount scrub). When you don’t disable automount Windows will signature all “incoming” disks. When this happens the VMware hosts will not recognize the VMFS volumes anymore. But fortunately you can re-label the luns as VMFS.

Check with “fdisk -lu” what the current ID value is of the volumes, it’s “SFS” if Windows wrecked it. Write all the devices down and label them again as VMFS:
fdisk /dev/sd? (? the letter for that specific volume)

p
d
n
p
1
default
t
fb
X
b
1
128 (disk alignment, check your SAN manual for the correct value, 128 is correct in most cases…)
W

Now rescan the HBA devices, esxcfg-rescan vmhba0 etc etc.