EMC's VMware unit is taking on HP with a Virtual Storage Appliance (VSA), building a small and medium business mini-SAN from servers' direct-attached storage.
The vSphere 5 launch included the in-house developed VSA, which combines storage directly attached to just three physical servers and combines it into a single (iSCSI) block-access storage pool accessible by apps running in virtual machines (VMs) in these servers. The pool is built up using VSA software running inside virtual machines (VMS) in the three servers, described as clustered by VMware but with no specific interconnect mentioned.
The storage in VSA is protected with synchronous mirroring across the nodes. There is a RAID 10 set-up in each node and RAID 1 across the nodes. If a single VSA node fails, the VSA process fails over to another node – and VMware says that VSA offers up to 99.9 per cent availability.
VSA is managed through vCenter Server and the installation process handles network set up and vSphere high-availability implementation. It also handles the installation and configuration of vCenter Server, vSphere as well as VMware VSA itself.
VMware VSA supports the Storage vMotion movement of apps between servers and to shared storage with no disruption of service access.
An additional limitation, apart from the 3-node cluster maximum, is that the VSA node count and individual server disk capacity cannot be changed once VSA is set up. A future VSA release should remove this restriction.
HP inherited its own VSA (Virtual SAN Appliance) when it bought LeftHand Networks in 2008. It has since extended the P4000 VSA so that it supports Microsoft's Hyper-V. HP's VSA can manage dozens of nodes and it has VAAI integration and a high-availability option, as well as thin provisioning. The data protection levels include Network RAID 5 and 6.
HP says its VSA is, presumably now "was", the only VMware-certified VSA, and it is Microsoft-qualified as an iSCSI SAN.
VMware is now competing with all of these.
VMware and storage arrays
VMware is increasingly taking on storage array controller functionality. The idea is to enable SMB-type customers, who don't have sophisticated storage arrays, to enjoy roughly equivalent functionality, such as array-to-array replication and, in VSA's case, a shared storage array in the first place, by using VMware and its host server's CPU cycles.
VMware will offload this functionality to shared storage arrays if they exist and, because VMware is owned by EMC, should not try to displace these storage arrays by emulating their expensive controller-based functionality with VMware software and cheap JBODs.
This wish to optimise VMware's storage offering with the whole EMC storage offering should limit the VMware VSA competitive affect on HP and other virtual storage appliance suppliers. They will have the Hyper-V VSA market to themselves and can, if they wish, use their VSA offerings to compete with low-end EMC arrays far more than VMware will be able to do so. ®