Eager zeroed thick virtual disk in ESX

This disk provisioning process fully allocating and zeroing out all the data inside the disk array at the time the disk is provisioned. This is an important distinction because a regular thick disk will require a short pause as its data expands to zero out data on the array. This isn't the case in an eager zeroed disk, where the space on the array has already been provisioned and the data zeroed out. The difference in performance between a thick disk and an Eager Zeroed thick disk is very small, but some applications, such as Microsoft Cluster Services and VMware Fault Tolerance, still require eager zeroed thick provisioned disks.

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Step-by-Step Explanation of Ballooning, Compression & Swapping in VMware

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Quick Guide to VCF Automation for VCD Administrators

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ESXi Host Troubleshooting Checklist

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