VCD and initial placement of virtual disks in a Storage DRS datastore cluster

Recently a couple of consultants brought some unexpected behavior of vCloud Director to my attention. If the provider vDC is connected to a datastore cluster and a virtual disk or vApp is placed in the datastore, vCD displays an error when the datastores do not have enough free space available.

Last year I wrote an article (Storage DRS initial placement and datastore cluster defragmentation) describing storage DRS initial placement engine and it’s ability to move virtual machines around the datastore cluster if individual datastores did not have enough free space to store the virtual disk.

I couldn’t figure it out why Storage DRS did not defragment the datastores in order to place the vApp, thus I asked the engineers about this behavior. It turns out that this behavior is by design. When creating vCloud director the engineers optimized the initial placement engine of vCD for speed. When deploying a virtual machine, defragmenting a datastore cluster can take some time. To avoid waiting, vCD reports an error of not enough free space and relies on the vCloud administrator to manage and correct the storage layer. In other words, Storage DRS initial placement datastore cluster defragmentation is disabled in vCloud Director.

I can understand the choice the vCD engineers made, but I also believe in the benefit of having datastore cluster defragmentation. I’m interested in your opinion? Would you trade initial placement speed over reduced storage management?

Comments

  1. says

    IMHO, it would be great to have an advanced option to enable support of defragmentation even if deployment would take (much) longer compared to usual time.
    Error in deployment will cause customer to send request to SP, what will cause manual job of vSphere administrator.
    From customers point of view it`s broken service, from SPs – need to regulary check free space on cluster disks.
    Either there is a risk that some customers can deploy\move to cloud very big VMs – the thing you cannot predict, what will either lead to broken service, from customers point of view.

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