Large Disks

Curious to get some feedback on any caveats (both architecturally and operationally) of using large disks that people may have run into. Environment info: vSphere 6.5, Zerto for DR (vSphere to vSphere), Commvault to back up our VMs and either Windows Server 2016 or 2019 for the VM OSes.

We have a file server migration project where some of the existing shares are 20TB (they are currently on a NAS) and growing at a rate of about 5-6TB/year. In the past, we used 20TB datastores and created 4-7TB virtual disks for each share and broke up the share content to “fit” into the smaller disks. Unfortunately, this resulted in the management of the smaller disks becoming somewhat labor intensive. In an attempt to avoid these issues this time around I am thinking of creating 64TB datastores with one single 60TB vmdk per datastore.

I’m looking for any positive or negative feedback on this idea along with any lessons learned from someone that has done or is currently doing this. I can think of some myself but I’m interested to hear what this sub thinks about this idea.


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  1. I have one 50TB and one 62TB volume. I’ve had those and other large VMDK’s attached to both 2016 and 2019 servers. Works great on Pure Storage. Zerto 6.5 was needed as 6.0 couldn’t handle VMDK’s of that size. Make sure to format your disk at at least 16kb (good for 32-64T). What do you have for storage? I’d recommend 2019 (I find it a little flaky yet, but still faster than 2016) or 2106 w/o a GUI. Current or newer VMware tools & compatibility at the highest in your environment and keep that current as you upgrade the environment. Also recommend using PVSCSI for those disks or NVMe when you are on 6.7u2 and if you have the storage behind it.

  2. I hate disks that big on VMFS datastores.
    Migrating them is a PITA and it’s next to impossible to “split” load across the backend storage.

    Multiple smaller disks are better to manage IMO.
    You could use a DFS namespace to hide away all those different paths.
    I get the data management part somewhat though. It’s a difference monitoring 10 disks for free space or 1.

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