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Scenario: SQL Server 2005 or 2008, Windows 2008 OS. Running in a VM hosted on VMWare ESX server.

Is there any known issue with VMWare when it caches pass-through write request and it never reaches the disk, while SQL Server "thinks" that write actually happened? This may lead to transaction log corruption in case of power failure or VM reboot. Just overheard the conversation but couldn't find it in relation to ESX.

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1 Answer 1

http://www.yellow-bricks.com/2011/04/07/mythbusters-esxesxi-caching-io/

So it is just writecaching inside your VM that you have to worry about, the same as if it was a physical machine.

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Found this link on VMWare : Storage IO crash consistency with VMware products : kb.vmware.com/selfservice/microsites/… it says "On Linux hosts, VMware does not use unbuffered IO ... When using buffered IO, VMware hosted products do not bypass the host's buffer cache to produce crash consistent virtual machine IO. Consequently, if the IO is buffered within the host operating system, an application running inside a guest operating system on VMware hosted products might lose crash consistency." Need to grasp it fully .... –  demp Aug 5 '11 at 13:36
    
That applies to products like vmware server rather than esx though. It is refering to the host OS not the guest OS. Esx is a baremetal host. –  JamesRyan Aug 5 '11 at 14:03

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