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EMC, VMware in 'furious high gear' over VAAI glitch

EMC and VMware are as close as two vendors can get, but that doesn’t make them immune to integration problems.

An issue with some versions of EMC’s Engenuity Symmetrix VMax disk array microcode and VMware vSphere’s vStorage APIs for Array Integration (VAAI) has EMC warning users of potential hits to performance and data integrity.

An unspecified but relatively small number of users have experienced performance slowdowns as a result of using EMC’s VMax arrays at certain microcode levels with VAAI, according to a blog post written yesterday by Chad Sakac, EMC’s vice president for the VMware Technical Alliance.

“When using VAAI for Storage vMotion and Cloning operations, performance degradation can result due to the the operation(s) taking longer to complete than when using Software (Host) Data Copy,” says an EMC knowledgebase article referred to by Sakac in his blog.

This is the opposite of what the APIs are intended to do: offload processing from the virtual host to the storage array to improve performance. There is also the potential for VM data to be inconsistent after a reboot following Storage vMotion, according to the article.

These problems have “popped up in enough places…that everyone at VMware and EMC went into furious high gear on this over the last few days,” Sakac wrote. There is now a patch called an Engenuity Pack — Engenuity is the name EMC gives to the microcode on its Symmetrix arrays — to prevent these issues on the VMax side, but customers must also contact VMware support for a hot patch to resolve the performance degradation issue with Storage vMotion.

Right now, it seems these are not widespread problems. Checks with VAAI users of other storage products this week haven’t yielded any reports of problems, and market reaction to VAAI in general has been tepid so far. The issue is a bit of a head-scratcher, though, given reports that EMC was among the VMware design partners for VAAI prior to the release of vSphere 4.1 last year.

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