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 vSAN you can use 2 different configurations based on your requirements which is Hybrid or All Flash. vSAN uses the Cache Tier and the Capacity Tier. Cache Tier is used for read cache performance while Capacity Tier makes the capacity for storing the data. In this post we will have a look at both of the models. In this post we will see on both the modes which are Hybrid and All Flash of vSAN.
As the Name suggests it is an Hybrid configuration of disks. vSAN Hybrid consists of the 1 SSD for caching and 1 or more HDDs for the Capacity. SSD will be used for the caching which consists of the Read Cache and Write buffer. So 70% of the SSD Drive will be used as an Read Cache for reading the data which will increase the performance while accessing the data and 30% of the SSD Drive will be used as an Write Cache. So when you write something on the VM that will be written first onto the 30% of SSD Drive then it will be destaged into the Capacity Tier.
In Hybrid HDD Drives are used for the Capacity Tier. HDDs basically means for the increasing the capacity and storing the data. All the data of the VM’s and other are stored in the Capacity Tier. Capacity Tier consists all the HDDs available in the ESXi Hosts.
Hybrid Mode can help in achieving the performance improvement as because the data reading is done from the SSD drives (Read Cache) instead of the HDDs drive from Capacity Tier. Hybrid mode can also help in lowering the cost of the purchase as you don’t have to spend much on the SSD Drives. Hybrid you can use 1Gbps Network is required if 10Gbps is used then it can be used in shared mode.
vSAN All Flash:
As the Name suggests it is an All Flash configuration of disks where all the SSDs will be used for the Cache and the Capacity Tier. There will be No HDDs in this configuration. vSAN All Flash consists of the 1 SSD for the Cache tier and 1 or more SSDs for the Capacity tier. There is no Read Cache available in All Flash configuration as data is directly read from the Capacity tier which are already SSD so you will get the performance boost.
Cache Disk in All Flash will act as an write buffer only so data is written directly to the Cache tier and then it will be destaged onto the Capacity tier. Capacity tier will consist of all the SSDs available in the ESXi hosts.
All Flash is always an recommended solution from the VMware because it boosts the performance of data read and write which is directly from SSD Drives. If you compare it with the Hybrid you will get far better performance improvement in All Flash. All Flash comes with the additional cost as it requires all the SSDs in the server. So If you are going with All Flash you will need to increase your budget but that will always give you the returns in terms of performance.
vSAN Hybrid does not support the Raid 5/6 (Erasure Coding) and Deduplication and Compression. All Flash configuration will support all the features of vSAN. vSAN All Flash requires dedicated 10Gbps Network.
Before going with any of the configuration make sure to check with the compatibility of the hardware devices.
VMware provides the vSAN Ready Nodes which comes in both the type of configurations Hybrid or All Flash. vSAN Ready Nodes from VMware are the certified configuration and completely supported. There are multiple configuration options available for vSAN Ready Nodes either it can be Hybrid or All Flash. There are multiple OEMs available of your choice so you don’t have to worry about the OEM Selections.
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