You cut the power to your ESXi with VMFS running on a RAIDAdapter with WriteCache on without a BBU What happens next?

I’ve been quite busy the last couple of weeks with building my own ESXi production machine.
After reading a lot about the different RAID/storage solutions and how dangerous enabling Write cache on a BBU-Less RAID
controller is, I decided it was time for a little experiment…

Ingredients
swechef1
Take the following ingredients
1 HP ML 110 G5
1 IBM ServeRaid BR10i
1 ESXi 4.0 U1
1 SBS 2008 VM
1 SBS 2008 VM Installing

Why on earth would I put an IBM ServeRaid BR10i inside a HP ML 110 G5? Well, maybe because I’m all about love, peace and happiness or maybe it’s because I got it from work because they use REAL RAID adapters there, nobody will ever know!
esxiproject-raidstatus-warning
Anyway, I played with the ServeRaid BR 10i for a while. As you can see the Adapter works great in ESXi. The status of the RAID
is being show in the VSphere client without any extras installed. (+1 for the CIM clients)
The first time I tried to upload a ISO to my Datastore using the Excellent VEEAM FastSCP, I almost fell off my chair. With a tortoiselike speed of 3-4 MB/s, my ISO was being dragged over the network.
So off to the VMWare Community website, where I found this thread which talks about using the LSI util to enable the WriteCache
option of the ServeRaid 10BRi (which is a rebranded LSI adapter). I’ve compiled the util so that it can be used on ESXi, You
can find it here!

Enabling WriteCache
You can enable the WriteCache of the LSI Adapter by doing the following:
After downloading the tool, use a tool like WinSCP to copy the lsiutil to your ESXi machine
Enter the console of your ESXi Machine or use SSH
chmod +x lsutil
./lsiutil
Then choose the following options
1
21
32

Enable write caching:  [Yes or No,]
Type Yes
Leave the rest default
Press 0 3 times to exit the util
After changing these options you can start the tool again and if everything went according to plan the Volume Settings should be set to write caching enabled!

I rebooted the ESXi machine to check if the settings would stick and they did!

SCOTTY,HOW FAST CAN SHE GO?
I started FastSCP again and uploaded the same ISO to my datastore, the upload speed changed from 3-4 to 22-23 MB/s !!!!!!!!
An 6x speed increase, again I fell of my chair but was more than happy to get up this time!

THE RISK
After reading the thread I mentioned earlier, I began to doubt my actions. What would happen to the VMFS and my VM’s if the power would be cut from my ESXi?
I didn’t sleep very well that night, even though my ESXi machine is behind a UPS the question kept haunting my mind.

TAKE THE POLL
So I decided to bite the bullet and test this scenario. I’m very curious what you think would happen so please take the poll below BEFORE watching the video below.
With corrupt I mean the VM is damaged in a way that you cannot access the vmdk files any longer. With crashed I mean the VM won’t boot because Windows crashed.

THE EVIDENCE
Now without further ado, I present the video:

Running VM’s on ESXi with a ServeRaid 10BRi LSI RAID with writecache on without BBU and then cutting the power from Virtualistic.nl on Vimeo.

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TAGS VMWare, ESXi, RAIDController, BBU, Performance, BR10i, LSI, LSIUtil