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VSphere 5, SSD disk for extra boost HP Microservers ESX?

janhoedt
janhoedt asked
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Last Modified: 2012-02-15
Hi,

I have 3 HP Proliant Microserver in a cluster with a Synology NAS DS1511+ as NAS.
Now performance is not great therefore I'm looking for ways to speedup performance.
Now I heard of the (new?) possibility to add ssd-disks into the server to which swapfile could be brought?
Any idea how this exactly works and how to configure + how big my ssd-disk would need to be then (I have 8 GB of RAM = 8 GB SSD?).

Thanks for your input.
J.
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Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
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The technique of memory overcommitment in a virtualized environment can help mitigate the problem, and using SSD to handle memory overcommitment can produce better results at a lower cost than memory overcommitment on mechanical disk.

SSDs can essentially become another tier of RAM in a server that can be used by virtual machines. Memory resource controls in vSphere can be used to guarantee or limit the amount of physical memory that VMs can use so you can effectively control when VMs swap to disk. Setting a memory reservation will guarantee that a VM will always have a specific amount of physical memory allocated to it; setting a memory limit will restrict the amount of physical memory a VM can use. This enables you to ensure that critical VMs have access to faster physical memory and that the SSD RAM tier is used by less important VMs once physical memory is exhausted.

Yes, we use Corsair and OCZ consumer SSDs in our Microservers.

There is an option under configuration for Host Cache Configuration.

ESXi can detect an SSD.

See here for further details

http://www.yellow-bricks.com/2011/08/18/swap-to-host-cache-aka-swap-to-ssd/

http://tinkertry.com/vsphere5hostcacheconfiguration/

How large an SSD you require depends on how much SWAP space you need to allocate!

But 60-120GB SSDs can give good benefits.

But Remember the MicroServer is only SATA 2!

Author

Commented:
Thanks!
Your remark "But Remember the MicroServer is only SATA 2!"
=> I'm booting from USB and even heard I can remove the USB once booted ... not tried it though so local disk shouldn't matter I guess.

Author

Commented:
However, I'm really interested how to implement it into the microserver (as they all have only 8GB).
Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
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Yes, what I mean is that most SSDs are now SATA 3, and best performance is obtained at SATA 3. (6G). e.g. Max IOPs.

In our tests SSD @ SATA2 speeds versus 7,200 SATA2 rpm disks can be the same!

You are certainly not going to see the real performance of a SATA 3 SSD are SATA 2 speeds, connected to the Microserver SATA 2 controller.

Author

Commented:
So just use internal disk of micriserver as swap?
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Ok, practically, for home lab: what would be best budget boost? Adding cheapest ssd available and set esx swap to it? Note: I boot and run from usb, didn t here any comment on that performance wise ....
Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
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Where ESXi boots from does not matter. It reads the contents from the boot disk into RAM, and then on shutdown writes the contents back.

So faster boot device = faster boot, faster VMware Tools Install, faster write at shutdown.

Basic SSD, set as Host Cache will certainly benefit via SATA2 hard disk.

Author

Commented:
Ok, thanks.
But please clarify, I still isn't clear to me what to do.

Basic SSD, set as Host Cache will certainly benefit via SATA2 hard disk.
=> I add a basic SSD disk (basic ones are 60 GB), it will be recognized automatically as SSD and I add all diskspace (60 GB) as cache? This will boost performance or not?
SSD (even the smallest ones) are not that cheap to just add them and see what happens. If it's not worth the effort I won't do it.
Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
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if you SWAP is in Host Cache, it will be faster than conventional hard drives, even 60GB SSDs.

Using conventional SATA 2 controller, I'm not sure what performance boost you are expecting?

Performance Boost expectations to me, could be different to you!

Remember the HOST Processor is only 1.3GHz!

Putting a Porche Engine in a VM Beetle, does not make it a Porche!

Author

Commented:
But it will ride as hell ;-)

You always refer to my local disk, but I'm not using it at all. I'm booting from USB.
I'm not expecting it to fly, I just want to tune my system as much as possible.
So I add SSD's and use them as cache? That's it?

Can you advise me which disks to take? I saw an article which mentioned a whole config to make it work (SSD cache) and don't feel like going all that trouble if that's the case (or do I just need to upgrade to latest patchlevel?). If it doesn't work out of the box, VMWare didn't put time or effort in it and doesn't really wants users to use it I guess.
Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
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Commented:
if you add an SSD, Corsair or OCZ consumer SSD 60GB, this will be much faster than conventional disk, configure as host cache and use for virtual swap, this will help your virtual machines.

Author

Commented:
I wonder: what is used as swap in my current config?
Local disk is not used, boot is frim usb ....
Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
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the virtual machine SWAP file is called .vswp and its located in each vm folder when the VM is powered on, on the VMFS datastore!

Author

Commented:
Wright! So even if I'd put the swap on slower sata disks, speed will increase!
Now I m again confused: you have the optuon to stire swap together with vm or somewhere else. What makes this swap different from generak server (ssd) swap? The fact its ssd, so it don t wirk with other disk types?
Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
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two functions here

currently you can change the vswap location of a VM to any datastore, this could be a really fast datastore e.g. SSD, this would create e.g. a vswap file = to current memory or reservation size.

OR use host cache configuration, which will use some of the SSD, because only active pages are swapped to SSD at a time, so you can allocate less SSD space.

which you use is upto you. Better use of space is achieved with the latter.

host cache only works with SSD. although unsupported hacks are arround to complete this on standard hard drives.

relocation of swap file, relocation of swap files can be configured for any valid datastore.

Author

Commented:
Ok, found the option to store on a specified datastore. However, the recommended option is to NOT do this. So why is that?

2 final questions:
-------------------------
1.if I set it on local disks of ESX, will it increase performance? I have only 1 NAS (Synology DS 1511+) with all vm's + other data so local ESX-disks look more performant to me
2.will it impact stability of vm? f.e. crash of ESX = corruption of vm etc?
Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
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Commented:
its not recommended on the basis, you could need lots of storage, thats why host cache was designed, because it uses less storage.

if your local storage is faster than nas, you may see a performance gain.

as for stability of VM. should not be affected.

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