Upcoming storage features in vSphere 5 have captured user interest. These features offer the potential to automate shared-storage management in virtual environments and allow movement of virtual machine (VM) data between disparate arrays. But some users say they'll wait to see how the new features will integrate with existing storage products.
Storage Distributed Resource Scheduler, or Storage DRS, was previewed at VMware's Partner Exchange conference in February. According to a detailed document leaked last week on the vSphere 5 release candidate, Storage DRS could ease and improve automated storage management in virtual environments.
The leaked document, which has since been removed from the Web, also alludes to "policy-driven storage delivery," which appears to be the incarnation of new application programming interfaces (APIs) extended to storage partners previously known as VMware-Aware Storage APIs (VASA). Policy-driven storage delivery "enables virtual machine storage provisioning to become independent of specific storage available in the environment," according to the document.
Ersatz storage tiering
The big win for Storage DRS could be to "extend the functionality of high-end SANs [storage area networks] down to people who can't necessarily afford them," said a U.K.-based partner, Chris Dearden, who requested that his company not be named. "It's got potential, and I'm certainly looking forward to it."
Consider, for instance, the Fully Automated Storage Tiering (FAST) feature on EMC Corp.'s high end arrays like the Clariion CX-480. "EMC's entry-level platforms don't support FAST tiering," said Michael Passe, a storage architect at Beth Israel Deaconess Medical Center (BIDMC) in Boston, Mass. Storage DRS could potentially enable FAST-like features "on any kind of storage you want," including smaller arrays for remote offices.
It's also not out of the question that even large shops with advanced and potentially overlapping array features could move VMs to separate, smaller arrays compatible with Storage DRS, Passe said. With 12 TB of storage attached to a single VMware server farm in his environment, Passe said putting all that data on one array that has integration with features like vStorage APIs for Array Integration (VAAI) and Storage DRS may be worth the headache of migrating the data.
"I like the capability of the software … doing the tiering," said Brandon Worrell, director of business development for Solutions II, a VMware partner in Salt Lake City, Utah. "[The software] has more intelligence about what's going on and understanding what the workload looks like than even the storage array."
Of course, storage administrators are known for being conservative, and they could resist the new features. But Bob Plankers, a virtualization architect at a large Midwestern university, said he's persuaded his storage team to try out things like vSphere 4.1's VAAI to improve management of storage and the virtual environment. "What won some of [the storage staff] over was less of my complaining about their array performance," Plankers said.
As with VAAI, Plankers said he thinks Storage DRS can find a home in his shop, even if it will take it a while to "burn in," as it will "require rethinking of how storage works under [virtual] environments," Plankers said.
Stepping on storage toes?
For other virtualization and storage pros, the jury's still out.
"It does seem like it has its benefits," said Phil DeMeyer, an information technologist at an early-childhood education program in the Midwest, which currently uses a SAN from Dell Inc.'s subsidiary Compellent Technologies Inc. Compellent's Storage Center SAN offers automated block-based tiering of data based on performance. "But I don't know that in our small situation that it would help us out at all. I'm able to do a lot from our storage-vendor side to handle a lot of situations that we run into."
Added DeMeyer, "Right now, Compellent has integration into vCenter, so I can do a lot of my storage management there. I think [Storage DRS] is something that I'll probably keep a careful eye on but I don't know that I'll ever really fully use it as much as [VMware] would like me to."
"Hopefully these new APIs will have integrate with [automated] storage tiering [features] so they can [all] work together," said Worrell. "If not, storage DRS isn't going to be used as much, because you'll have to turn off the storage tiering and lose some of the functionality you're paying money for, or it might be one of the reasons you purchased that particular storage array."
Devil's in the details
Questions also surround how the nitty-gritty underpinnings of the new features will fit and work together, even for those attracted to the concept.
Virtual machines whose Virtual Machine Disk (or VMDK) files are striped across multiple logical unit numbers (LUNs) or that reside on shared volumes, for example, could present a 'gotcha' to Storage DRS, should it assume a one-to-one relationship between VMs and LUNs on shared storage. Although, some users say this situation is a relatively rare use case. "Out of 500 VMs I have, there are four that fall into that category," Plankers said.
Wondered Worrell, "Just like with some of the VAAI stuff, if Storage DRS did have to happen, or if vSphere detected that it should happen, can the storage array do that more efficiently than the software stack doing the DRS call? I'm excited about it. I think it'll be a great thing, as long as it's fully integrated."
Beth Pariseau is a senior news writer for SearchServerVirtualization.com. Write to her at firstname.lastname@example.org.