SSD Cache

[TheVMEvolution]

Does VMWare ESXi support SSD caching to improve Disk I/O?

[TheVMEvolution]

I know Citrix Xen supports something like this, I believe its called IntelliCache but I could be wrong

[realdreams]

Is that even ESXi related? OP is asking vSphere ESXi 5

[Zhuominchen]

Does VMWare ESXi support SSD caching to improve Disk I/O?

Yes at two levels

1) Host cache on SSD  :  This is used when you give more memory to guests than physical memory

2) Guest's Swap Space  on SSD (vs on same directory as vmdk)

  :  This is when Guest applications use more memory than each guest is configured to consume.

FYI: Whatever you do with vsphere-client actually happens on ESXI server side.  

[mcowger]

1) There is no such Host Cache on SSD option.

[Zhuominchen]

Vsphere Client

Highlight left top nod.

Configuration.(under software).Host Cache Configuration 

You can only use SSD for this.  Default Host Swap Cache is at

OS disk partition.

Jimmy

[mcowger]

Thats for SWAP only - not general storage access, which is what the OP is referring to.

[Linjo]

Host cache does not directly improve disk performance, its for the ESX to swap out from memory in case of oversubscribtion.

Indirect this can have an effect since you normally would swap this to spinning disk in a slower rate and this IO is now gone.

// Linjo

[Zhuominchen]

Sorry I misunderstood original post.  

You guys are correct.  Vmware SSD cache is LAST hit-device, thus does nothing to improve I/O.

I jumped on it because I thought it was like zfs L2ARC (first hit-device). What disappointment. 

Jimmy

[eeg3]

A new feature of View 5.1 is the "View Storage Accelerator" aka "Content Based Read Cache". Not sure this can be used outside of the VDI environment, though. This puts storage into memory instead of SSD.

[mcowger]

Its limited to 2GB, and View use only.

[TheVMEvolution]

I'm basically using 4x local drives in hardware RAID10 now, and want to achieve better Disk I/O in my containers in VMWare. Intellicache for Citrix Xen does this and you can put something like a 60GB SSD for Intellicache, then it improves read operations (not write, but by offloading reads to an SSD cache it will improve write speeds).

So that is what I'm trying to accomplish, does VMWare ESXi offer something like that?

[mcowger]

Not today, no.

[rickardnobel]

TheVMEvolution wrote:

I'm basically using 4x local drives in hardware RAID10 now, and want to achieve better Disk I/O in my containers in VMWare.

In ESXi 5 there is the feature of "SSD Swap Cache" which could use local SSD as a first-hit instance before going to mechanical disk. However, as the name implies, it is only for VMkernel swapping and not for general disk access.

[Zhuominchen]

I just found this feature, which allowing guests to use SSD as swap device DIRECTLY.

on Vsphere client

1) Highligh Hosting Node

2) Click  Configuration

3) Click on "Virtual Machine Swapfile Location"

4) change from your OS drive to SSD

On Guest setting, use  Swapfile Location "Default"  , which is

same location as hosting server swapfile location (SSD), assuming

that you already setup "Host cache" to SSD.

Now you can do memory-overcommit without worrying bringing down other guests.

Jimmy

[TheVMEvolution]

Thanks for the information. What are the chances in your opinion that VMWare will support something like Intellicache in the future?

I appreciate your responses.

[mcowger]

Personally?  I would consider it doubtful - they wouldn't want to alienate their vendor partners too much, most/many of whom already provide similar functionality within the array (where its more effective than in-host).

[TheVMEvolution]

I understand. Will the "View" with 2GB cache help what I'm trying to accomplish at all?

[mcowger]

No - it only work if you are using VMware View.