VMware Storage Blog

With the launch of vSphere 4.0, VMware introduced a new version of the ESX Server and the management server, vCenter Server. In addition vSphere enables greater resource efficiency, management control, and freedom of choice for virtual datacenter storage resources and connectivity options. A brief summary of these new storage management capabilities in vSphere 4.0 are as follows:

Virtual Disk Thin Provisioning

Virtual disk thin provisioning increases the efficiency of storage utilization for virtualization environments by dynamically allocating storage and using only the amount of underlying storage resource needed to store the contents of the virtual disk.  On average customers feedback is that they expect a reduction of 50% of their storage space. 

Improved iSCSI Software Initiator Efficiency

The new vSphere iSCSI SW initiator has been optimized for virtualization IO and provides significant improvements in CPU efficiency and throughput when compared to the earlier 3.5 version. VMware has released a new iSCSI software initiator that is far more efficient in its use of the ESX CPU cycles to drive storage IO. The entire iSCSI software initiator stack has been tuned to optimize cache affinity, enhance VMkernel TCP/IP stack, and to make better use of internal locks.

New vCenter Server Storage Enhancements

To help manage storage space in vSphere, each VM and ESX in the inventory now has its own storage tab that shows information about storage resources for those objects. The datastore can now be also managed as an object within vCenter in a manner that allows the vSphere administrator to view, group, and set permissions for each datastore. vSphere also provides a detailed view of all the components in the storage layout .These topology maps provide key information to administrators about which paths are available, as well as the grouping of objects sharing storage resources and new alerts and alarms are a key capability for to effectively managing datastores in which thin provisioned disks might create an over allocation of storage resources.

Enhanced Storage VMotion

Management of Storage VMotion is now fully integrated into vCenter Server. It offers full support to move a VM home from one datastore to another to facilitate storage migration. Some of the use case for the migration can be changing the storage protocol (FC, iSCSI or NFS) and/or change from thick to thin virtual disk format without impacting the VM.

In vSphere, Storage VMotion is also significantly more efficient because it leverages a change block tracking method that moves the VM home over to the new datastore much faster than in snapshot method used in the ESX Server release 3.5, and it no longer requires twice the CPU and memory of a give VM.

Dynamic Expansion of VMFS Volumes

VMFS Volume Grow offers a new way to increase the size of a datastore that resides on a LUN that has been recently increased in capacity, via the vSphere Client GUI without disrupting the running virtual machine. It complements the dynamic LUN expansion capability that exists in many storage array offerings today. If a LUN is increased in size, then VMFS Volume Grow enables the VMFS volume extent to dynamically increase in size as well.

 vStorage APIs for Multipathing

In vSphere, leveraging third party storage vendor multi-path software capabilities has been introduced through a modular storage architecture that allows storage partners to write a plug-in for their module to leverage. These modules can communicate with the intelligence running in the storage array to determine the best path selection, as well as leveraging parallel paths to increase performance and reliability of the IO from the ESX to the storage array. By default the native multipath driver (NMP) supplied by VMware will be used. It can be configured to support round-robin multipath as well. However, if storage vendor module is available, it can be configured to manage the connections between the ESX and the storage. There are three types of plugins, Path Selection Plug-in (PSP), Storage Array Type Plugin (SATP) and Multi-Pathing Plug-in (MPP.)

Conclusion

VMware is now providing more storage options and features that provide greater control, choice and efficiency to be leveraged in a vSphere environment. The new storage features, as well as previously existing ones (like VMFS) are grouped into an infrastructure category named vStorage. vSphere 4.0 enables the vSphere administrator to do more with less.  Extending the benefits provided by virtualization reach new levels of storage efficiency, management control and additional choices in storage connectivity. To read more on the new features in vSphere see the What’s new in vSphere - Storage paper, for detailed information on configuring see the Configuration Guide.

Authors: Paul Manning, Sr Technical Marketing Architect &