In addition, the new version of i5/OS due out next year will be able to support the VMotion feature of VMware ESX Server. This will allow a user to do a live migration from a VM on one System x server to a separate System x server while using the System i as the shared storage target.
IBM made the announcement quietly two weeks ago, but attention to its Redbooks Residency program -- which allows developers dispersed around the globe to collaborate as they write manuals on future IBM technologies -- has drawn speculation about what VMware support would actually mean.Delving further into the SMB market
Owned by storage giant EMC Corp., VMware of Palo Alto, Calf., is the largest provider of server virtualization software for x86 machines, including IBM's System x and BladeCenter. But VMware does not yet run on machines other than x86 servers, so IBM's Redbooks Residency program announcement titled "Running VMware ESX Server on IBM System i" had some wondering whether VMware was developing its software for other platforms.
"This was not an announcement that VMware ESX Server will run on System i," said Jon Bock, VMware's senior product marketing manager. "It means the [System x] could access storage that is part of the System i deployment. Say I have a customer that has an iSeries deployment, that's interested in virtualization on the xSeries but has a lot on the storage side in iSeries. By providing this capability to the iSeries, the customer won't have to have separate storage for iSeries and xSeries that VMware ESX Server is running."
Chris Wolf, an analyst at Burton Group in Midvale, Utah, said this feature would be attractive primarily to those small and medium-sized businesses (SMBs) where System i not only runs a company's mission-critical applications but also serves as its main or only storage device. Although larger enterprises might take a look, Wolf said they already have high-end storage arrays in place and probably don't need to rely on System i for storage.
Clay Ryder, president of analyst firm the Sageza Group Inc. in Union City, Calif., agreed, adding that it's another feature of System i's ability to connect and manage System x through iSCSI.
"At a very basic level, it's another arrow in the quiver of System i's management functionality," he said.
IBM System i product manager Kyle Wurgler said the storage support for VMware would mostly be for SMBs but could also fill a gap in larger enterprises when necessary. Typically the types of customers using the iSCSI connection between System i and System x have between a couple and 100 x86 servers.
"Typically those customers either don't have a SAN (storage area network) today or they've had a SAN and they're a little bit tired of managing it," he said.Reliable workload balancing
How does it work? First, System x servers will connect via iSCSI to storage resources within an IBM System i box (see figure below). Your System x servers must then run VMware ESX Server.
This graphic shows how System x servers can be connected to System i via iSCSI:
Meanwhile, the next version of i5/OS will include support for VMotion, a feature that allows users to migrate a VM from one server to another physical server without any downtime. This allows users to balance their workloads between physical servers depending on what applications are busy at a certain time, as well as providing some failover benefits and allowing administrators to do maintenance on one server without the virtual image going down.
This graphic depicts how VMotion works:
System i comes in on the storage side. In order for VMotion to work properly, you need to provide shared storage between the two System x servers. So System i -- just like any other storage device from EMC, Network Appliance Inc. or anywhere else -- will act as the shared storage for those two servers.
Shared storage is critical when doing a live, or hot, virtual machine migration from one physical box to another, as VMotion enables the migration of the virtual image but not of the underlying storage. As such, both the source and destination System x or BladeCenter servers have to point to the same storage device.
"What's on disk could be 150 gigabytes or whatever," Bock said. "We rely on that storage being the same so we don't have to carry that storage live. That would be much more complicated."
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