6.19.2015

vSphere (and others) LAB storage

Some of you may know I have been building and using a vSphere lab for a number of years now as most VMware professionals. Recently the SAN platform I've been using for a couple years, Nexenta, has removed/disabled VAAI support from their software because of some issues so I decided to try the other popular FreeNAS since it's been rapidly maturing.

For the most part my 3 Nexenta SANs have been running fine until a HDD dies at which time the SAN would lock and require some coaxing and perhaps a power cycle to come back alive. With some of the recent changes to the platform, removing VAAI, I decided it was time to give FreeNAS another try.

For those of you involved in some way with VMware vSphere you know that VAAI was a very important advancement in storage function and management. It provides primitive functions to allow the storage controller to do the work only sending progress updates to the hosts cutting down on latency and storage fabric utilization. Nexenta used to provide 3 of the commonly used and 1 of the uncommonly used primitives. https://v-reality.info/2011/08/nexentastor-3-1-adds-second-generation-vaai/
They have removed VAAI in the recent patches 4.0.3FP2 due to "kernel panic issues". What they failed to realize is this is a SIGNIFICANT change to a storage infrastructure. It's easy to introduce from a traditional non-VAAI design but once a storage architecture is designed for VAAI it's nearly impossible to go back. FreeNAS 9.3 supports 5 primitives, you get a bonus one. http://www.ixsystems.com/whats-new/freenas-93-features-support-for-vmware-vaai/
1 particular primitive, ATS, allows us to make LUNs much larger in size since only VMDK operations happen at the file level instead of the entire LUN. This allowed us to make larger LUNS since having more then 10 or 15 VMs in a LUN since the host would not lock an entire LUN for a single file operation causing the rest of the VMs to be impacted. Further FreeNAS also includes Warn&Stun which provides the host with some more intelligence about a thin provisioned VM reducing crashes.

FreeNAS has also been making many other improvements to the platform. One major one was the migration from iSCSI target software being moved from user space to kernel space. After some 'seat of the pants tests' compared to earlier releases this seemed to provide a nice 30% improvement in performance.

Installing 9.3 FreeNAS is as simple as it's always been, a couple presses of <ENTER> and it's installing. One nice feature is you have the ability to install to USB where Nexenta cannot. However make sure you create SWAP on a disk once you have it installed. Being BSD based compared to openSolaris you have a much wider array of hardware choices. Going from Nexenta to FreeNAS you should have no issues. The community forms and docs provide some good direction for hardware and firmware versions. For example using the standard LSI HBAs you know to use the P16 firmware version. The other cool feature is FreeNAS does not limit you to 18TB of RAW storage.


I've now been running FreeNAS as the main LAB storage san for a couple days now and I'm rather impressed with it's performance and stability. Nexenta, I couldn't always say this...

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