VMware users tepid on vSphere's storage array features

VSphere 4.1's new storage array features could alleviate serious I/O constraints for large IT shops, but users are in no rush to retool their environments to use them.

Big VMware shops with I/O constraints could soon get a break. Their storage arrays will soon be able to take over much of the storage processing that currently happens on ESX hosts. With vSphere 4.1, VMware has issued vStorage APIs for Array Integration (VAAI) to storage partners with the goal of solving common storage management headaches.

But users say they won't rush out to upgrade storage arrays to take advantage of the new features. Meanwhile, the Palo, Alto-Calif.-based VMware Inc. continues to walk a political tightrope with its hardware partners with the rollout of the application programming interfaces (APIs).

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VAAI features a nice-to-have 
The new vSphere 4.1 features under VAAI include Full Copy Offload; Block Zeroing and Scalable Lock Management, all of which are designed to improve performance. As the name implies, the Full Copy Offload feature offloads the processing of full-volume copies to the disk array instead of using host-CPU cycles and memory; Block Zeroing reduces the number of repetitive commands representing empty blocks that are sent from the host to the array during a copy process; and Scalable Lock Management, which offloads the processing of SCSI reservation locks to the storage array. VMware and partners have also previewed a fourth feature, Thin Provisioning Stun, though this functionality was not included in the official 4.1 release. Reportedly the feature is designed to send a command from the disk array to the host that pauses virtual machines in the event that a thin-provisioned volume runs out of space.

Scalable Lock Management will appeal to users in very large environments, especially those with applications that use block storage, which involves a lot of small I/O. VMware has worked to hone SCSI reservations to cut down on contention in large-scale environments since version 3.5, but as of last year's VMworld, a group of VMware engineers warned users that at large scale, such problems may still exist. The VAAI integration would allow storage arrays, which have more scalable and granular locking mechanisms, to handle the process, rather than the Virtual Machine File System (VMFS).

There just isn't value enough to take a risk.
Nasser Mirzai,
senior director of ITTradeBeam Inc.

"I can definitely see it being a gain if you have particularly busy VMs sharing volumes under VMFS," said Eric Parson, a senior systems support engineer at Chicago-based wireless service provider U.S. Cellular, though he said it hasn't been a problem in his environment.

But while users say they understand the value of the new features, most traditionally conservative storage buyers say that it would take six months to a year to modify their environments to accommodate these features, even if every storage vendor had all the features ready today. "There just isn't value enough to take a risk," said Nasser Mirzai, the senior director of IT for trade management software and service company TradeBeam Inc. in San Mateo, Calif. TradeBeam currently has about 200 VMware guests, but plans to spin up hundreds more by the end of the year, " Mirzai said. "I just don't see anything that says, 'I must do this,' and I don't want to make a firmware or forklift upgrade unless I have no other choice."

Furthermore, the kind of integration promised with VAAI is a long time coming, said Randy Weis, a senior solutions architect at GreenPages, an IT solutions provider in Kittery, Maine. , During that time, users in large storage environments have already had to adjust to those conditions and thus won't be busting down doors to add it. "I haven't heard users saying, 'I have to get an array that has that,'" he said. Timeout and locking issues have become "part of the landscape. If you live in the mountains, it snows; if you use block-level storage, you have to deal with file locking."

VMware plays partner politics in the storage market
At times VMware has had a bumpy road in its relationships with ecosystem partners, including with storage hardware partners that believed VMware had reinvented their wheel with VMFS and Storage VMotion. Storage vendors also complained that VMFS was a black box that didn't give visibility into virtual machine files for common operations such as data replication and backup. VMware's response was a more granular set of APIs developed for vSphere, addressing both array integration and data protection.

But now, according to multiple storage industry sources, VMware has given some vendors preferential treatment with VAAI. EMC Corp. (VMware's parent company) and NetApp Inc. were the first to receive the API code in a software development kit (SDK) from VMware in January, while others received it the next month or later -- and amid a vast number of disk array manufacturers in the market, many still have not received it at all. This has prompted new grumbles among VMware storage partners about perceived favoritism.

"[EMC and NetApp] were the only two companies that got the SDK early enough," said one storage industry source. "When the launch came up, it became clear that some would be able to stake claims others couldn't ... with [EMC CEO Joe] Tucci's boasting on [a recent] earnings [call] on EMC having the most VMware APIs in the industry, it annoys folks when things like this happen. "

VMware did not specify when individual partners received the VAAI SDK, but did acknowledge a tiered system for rolling out the APIs. "When we created the VAAI, we worked with a group of design partners so that we could get the technology in a state where it would provide the most value to the broadest set of customers and partners," a VMware spokesperson wrote in an email to SearchServerVirtualization.com. The "design partners" named by VMware are Dell, EMC, Hitachi Data Systems (HDS), Hewlett-Packard Co. and NetApp. Combined, these vendors control the lion's share of the market for storage subsystems, but there are some notable absences, including IBM, IBM's OEM partner LSI Corp., thin-provisioning pioneer 3PAR, and an EqualLogic competitor in midrange disk arrays, Compellent Technologies Inc. Compellent has made hay with its VMware integration in the past, but HDS and HP have both announced major partnerships with Microsoft in the last year.

By the time most users are ready to upgrade to arrays that support VAAI, most storage vendors will be able to offer the same features. But some are made at least a little nervous by the potential for continued friction between VMware and storage partners.

"Depending on how they work with [partners] or not, if one gets upset, you'll start seeing the same sort of functions with KVM [Kernel-based Virtual Machine], maybe, or jumping on Hyper-V's bandwagon," said Tom Becchetti, a senior systems engineer at a large manufacturing company. Partners may say, "'OK, [if] you're going to do that, we're going to go work with Microsoft,'" potentially leaving users caught in the crossfire of shifting vendor alliances. "It could get interesting as this all shakes out."

Beth Pariseau is a Senior News Writer for SearchServerVirtualization.com. Write to her at mailto:mbpariseau@techtarget.com.

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