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I have a windows 2008 64 bit server running as a guest on VMWare ESXi 4 Update 01 build-208167 which runs on top of an HP Server with SAS RAID 5 disks. It is performing well with 3 GB RAM. I wanted more storage so I added another virtual disk to the VM. Formatting this disk in Windows 2008 is extremely slow. What could be the reason?

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Did you select the option to quick format the disk? – pauska Feb 16 '10 at 10:22
What do the VM's disk IO stats look like? – Chopper3 Feb 16 '10 at 10:28
@Erik I selected the regular formatting option – BuZain Feb 16 '10 at 11:12
@Chopper3 according to to the monitoring tool, Disk Write rate is Max 3989 KBps with average rate of 3334 KBps since I started the format command – BuZain Feb 16 '10 at 11:12
I just tried the quick format option and it was swift. I wonder why the regular formatting option is that slow ! – BuZain Feb 16 '10 at 11:32
up vote 2 down vote accepted

REgular formatting will zereo out the virtual disk, which be default is eager zeroed thin and not thick. This is optimal as your disk will be completely zeroed out and won't incur any I\O penatlies during writes. Another way to do this is to create an eagerzeroedthick disk first from the command line using vmkfstools and then use the quick format. Or do the quick format then power down and convert the disk - again using vmkfstools - to a eagerzeored thick disk.. I believe to convert it the command is vmkfstools -X /path to disk

But I will say this much, the full format is the slowest thing ever and I too would like to understand more on this becvause the same process in w2003 never took this long... it is ridiculous.

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