VMware vSAN is an software defined storage solution from VMware to eliminate the need of the additional storage boxes using the local server storage. In simple word vSAN abstracts the local storage of ESXi hosts & make a pool of it to be used as an shared storage which is very much optimized. So as you are using the local storage you will not need an additional storage boxes for the storing files which also helps in lowering the Total Cost of Ownership (TCO).
vSAN uses the local server’s disk to create an datastore . Disk in the server can be of multiple types such as SAS, NL-SAS, SATA, SSD , NVMe etc. In this post we will see on What is vSAN Disk Groups and what are the maximums of Disk Group.
vSAN Disk group is an logical container of storage where multiple disks are present. vSAN uses disk groups instead of single disks to form a datastore. Where all Disk Groups contributes storage and all are aggregated into one datastore.
vSAN Disk Group View:
As you can see from the above image that there is some limitations on vSAN Disk Groups. You can create maximum 5 Disk Groups per ESXi Host. Each Disk group must contain at least 1 SSD and 1 or more HDD Drives.
If you are going for the Hybrid mode then there will be 1 SSD for cache tier and 1 or more HDD for capacity tier in the Disk Group but if you are going with the All Flash mode then there will be 1 SSD for cache tier and 1 or more SSDs will be for capacity tier. When you enable the feature such as Deduplication and Compression they are enabled at the Disk group level.
When you deploy VM the disks of that vm is spread across the different disk group of different host so that you can tolerate the one host failure. If the Cache tier disk is failed then whole disk group is considered as an failed. If any capacity disk fails then vSAN will wait for 60 minutes to come back for that disk if it doesn’t comes back then vSAN will try to recreate the missing components and rebalance will occur.
By default there is 60 minutes time for the disk failure or the Host Failure vSAN will wait till the 60 min , In that time if the ESXi host or disk comes back vSAN will not rebuild the components but if doesn’t come back then vSAN will automatically start the rebuilding the components and rebalance cluster will occur.
As of now your understanding of Disk Groups in the vSAN Should be clear. In the future post we will be looking on How to create a Disk Group.
Checkout Our Posts on vSAN:
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