Zero Out Free Space

This is post #10 in my December 2013 series about Linux Virtual Machine Performance Tuning. For more, please see the tag “Linux VM Performance Tuning.” When we talked about the rationale behind storing logs centrally one big reason was thin-provisioned virtual disks. Those disks grow over time because filesystems on a virtual machine currently have no way to tell the underlying storage that they’re done using certain blocks on disk. There is a way to make these VMs thin again, and I wrote about it as step 9 in my guide to preparing Linux Template VMs. In short, we run a script on the VM that writes zeroes to most of the free space on the VM: #!/bin/sh # Determine …

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VMware & Virsto

Howard Marks has a great piece on VMware buying Virsto over at Network Computing (link is below): Some of my fellow analysts have lumped Virsto into the flash acceleration category along with caching solutions like Proximal Data, Sandisk’s Flashsoft and Intel’s CAS. While Virsto can use flash to accelerate some storage I/O, it’s not primarily a flash acceleration product. In fact, Virsto is a log-based, clustered file system that uses a dedicated log device, which can be a shared SSD, to accelerate virtual machine I/O. I saw Virsto for the first time at VMworld 2012, and it looked interesting as something that tries to turn a lot of the random I/O from a virtualization environment back into sequential I/O that arrays can better handle, while adding a …

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