dwisby
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Multiple Datastores

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I am needing to create an additional datastore and the first one I created with a 1mb block size. If I want to create the new datastore with a different block size, will I need to move all the VM guests to the new datastore and reset the block size on the first datastore or do I have to rebuild the volume and reformat with the new block size?

Thanks

David

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a_p_
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Well for storage VMotion the target datastore must have a block size which support the vmdk size. That's no question.

If you only have two datastores and you want to do storage VMotion, create both of them with the largest block size you need.

André

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a_p_
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David,

you can have multiple datastores with different block sizes. Just make sure there's only 1 datastore per disk/LUN.

André

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dwisby
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Thanks for the quick response. If the block size is different on the datastores and we use vmotion/vstorage it seems there would be issues if a vm with a large disk on the datastore with a larger block size was moved to the datastore with a smaller block size.

Hope this makes sense.

David

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golddiggie
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Only makes any sense if the vmdk file is too large to fit on the smaller datastore. I've vMotioned VM's from datastores that were 375GB in size to ones that were 500GB or 1TB in size (and the other way around too) without issue. Are you using vMotion to shift the files around or a different method?

VMware VCP4

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dwisby
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I was thinking that if I used vstorage and a vm with a 512Gb drive was needing to be moved to the datastore with a block size of 1Mb I would run into difficulties. So if I create datastores with the same block size, I would not have the problem. In the future I could see a guest with an iSCSI attached drive that may be larger than the 256Mb allowed by the 1Mb block size.

David

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a_p_
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Leadership

Well for storage VMotion the target datastore must have a block size which support the vmdk size. That's no question.

If you only have two datastores and you want to do storage VMotion, create both of them with the largest block size you need.

André

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dwisby
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Thanks for all your assistance. I will probably stay with the 1Mb block size and use RDM if I need larger disks for file storage. If later on I decide to use large iSCSI volumes for file storage on a vm I can create new datastores with larger block sizes and move everything to those datastores and delete the old datastores.

David

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