Vsphere Storage Appliance vs VMware VSAN

The Vsphere Storage Appliance

Introduced in 5.0, the VSA allows you to create a small cluster (2 or 3 nodes) using local storage and turning that local storage into shared storage. The VSA is managed via the VSA Manager (in the Vsphere Client) and controlled by VSAs (1 x host). These VSAs are linux based appliance which are created automatically when the VSA cluster is created.

The above example shows a built 3 node cluster. Notice that this cluster has 3 datastores (2 if built with a two node cluster).

The VMWare VSAN

Introduced in 5.5u1, the VSAN needs a minimum of 3 esxi hosts and a maximum of 32. It has functionality built into the kernel. The VSAN uses local and SSD disks (for caching and intelligent data placement) and allows for further scalability.

The above image displays how to select devices to be used by the vsan. Each host needs to have at least one internal disk and one ssd disk.

vSAN Limitations:

Despite the fact that vSANs are compatible with HA, DRS, snapshots, SRM and VDP, currently vSANs are not compatible with Storage DRS, DPM, FTand Storage I/O Control.

How to Configure Flash Read Cache on one Host

What it is:

Flash Read Cache is a new feature found in 5.5 to centralize the management and configuration of flash based devices such as pci-e flash cards or SAS/Sata SSDs. These local devices can now be used to enhance the performance of esxi hosts by storing the host swap file and read caching for virtual machines i/o requests.

Steps:

1. Launch the web client and log in as the administrator. You can't use the Vsphere Client for this.

2. Select one of your esxi servers and go to the the Manage tab.

3. Select Settings and click on Cache Configuration

4. Click on Add Capacity and Select the SSD drive to use. Then click on Ok

5. Once selected, the system creates a VFFS file system.

6. To configure a virtual machine to use the Flash Read Cache, right click on a virtual machine and select Edit Settings. Select Hard Drive 1 and expand. Enable Flash Read Cache and specify the Cache Reservation and the Block Size.

 

Note:  The Web Client in 5.5 allows for vmotion of vms with flash read cache. As you vmotion a virtual machine, there are two new choices that allow you to select "Always Migrate the Cache Contents" and "Do Not Migrate the Cache Contents".

Flash Read Cache esxcli Commands:

esxcli storage vflash

. module get
. module list

. cache get
. cache list

. cache stats get
. cache stats reset

. device list

ex:  # esxcli storage vflash device list