Esxi 5.5 treats ssd based array as non-ssd

Hi everyone,

I have just installed the ESXi 5.5 on our Dell PER710 server. It has a H700 controller with eight ssd drives in a RAID 10 array.

The ESXi claims that the datastore is "non-ssd" based. Because I am not exactly sure what are the implications of that, I wanted to fix it using the article below.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2013188

I went to the "Summary > Storage > Unmount" in the vSphere console before proceeding any further.

Then I added the "enable ssd" rule as per step five.

Unfortunately, when I reboot the server after adding the rule, everything stays the same.

When I try to "unclaim the device" as per step six, I get the following error:

"Unable to perform unclaim. Error message was : Unable to unclaim all requested paths. Some paths were busy or were the last path to an in use device.  See VMkernel logs for more information."

And needless to say, I am still getting "Is SSD: false"

I have tried to put the server to the maintenance mode but that did not help either.
Martin AndelSenior IT AnalystAsked:
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
This is because, when you have RAIDED the SSDs, the virtual disk, does not appear as an SSD anymore to ESXi.

As for performance, it will be exactly the same whether it's set to non-SSD or SSD.

BUT, SSD functions will not be available.

So were you going to use any SSD functions, or just use all the datastore as a VMFS datastore!

SSD functions include, Host Cache, virtual flash and vSAN. (and for that you don't want to RAID them anyway!)

I completed some EE Articles here

HOW TO: Tag and Configure a storage device as a Solid State Disk (SSD) in VMware vSphere 5.0 or 5.1  (ESXi 5.0 or ESXi 5.1)

HOW TO: Configure Host Cache Configuration for your VMware vSphere 5.0 or 5.1 ESXi (5.0 or 5.1) Host Server

If you are just wanting it as a datastore.... don't waste you time.

see also here

http://www.v-front.de/2013/10/faq-using-ssds-with-esxi.html

Please also be aware, other VMware Admins have also bunged in eight SSDs, and RAIDED them with RAID 10 and performance has been poor, compared to a single SSD datastore, e.g. NO RAID! - this is normal and to be expected.

Performance can be worse than standard SAS disks in RAID 10.Making assumptions SSDs are fast, so bung them all in RAID 10, and it will go super fast.... Just in case you find performance not as to be expected!

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Martin AndelSenior IT AnalystAuthor Commented:
Okay, that makes a lot of sense. We've set this up in raid 10 to get a performance gain, but shouldn't there be any, there's no reason to stick to it.

So can you please recommend a solution that would yield us maximum performance/storage space using the current resources? Perc H700 and 8x 512GB ssd's.

I cannot spend a penny more I am afraid :)
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Test you current solution, as 8 x 512GB SSDs versus a single SSD, in RAID 0, and two 512GB SSDs in RAID 1.

Also depends how many IOPS, and what performance you require.
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Martin AndelSenior IT AnalystAuthor Commented:
Right. And if we went back to the original plan of setting up a raid5 array and perhaps configuring one hot spare?

There would still be a fair amount of storage, increased redundancy and the speed achieved by the ssd's themselves rather than the raid controller?
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Yes, but I would TEST performance, before you commit, to any configuration.
Martin AndelSenior IT AnalystAuthor Commented:
What would be the best way to test the performance then? Can you please recommend any tool I could use? I already have the esxi installed on the RAID10 setup, but no guests on it.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Install a VM, and inside the VM, you could use

I/O Meter
(this is the benchmark used in the VMware industry)

http://www.iometer.org/

CrystalMark Benchmark

http://crystalmark.info/software/CrystalDiskMark/index-e.html

and DiskTT

http://www.snapfiles.com/get/disktt.html
Martin AndelSenior IT AnalystAuthor Commented:
Thanks, I'll do the testing and post the results when ready.
Martin AndelSenior IT AnalystAuthor Commented:
You were right on the RAID 10 being a bad idea. We did some extensive testing last night using the DiskTT and Crystal Disk Mark.

The results clearly show that on the RAID 5 scenario, there was a huge increase in the write speeds (almost a double at writing in small blocks) and only a marginal decrease in read speeds (about 5 to 8%). Also the 7 disk RAID 5 set-up yields 700GB more storage and we can afford having one hot spare.

The original concept of 8 ssd's in RAID 10 was nowhere near as efficient, yielding only 2TB (as opposed to 7.2TB on RAID 5) of storage space and no hot spares.

My only worry now, is how quickly will the ssd's wear out as the H/W raid doesn't do TRIM and the ESXi itself does not recognize the array as ssd-based.
Martin AndelSenior IT AnalystAuthor Commented:
Thanks!!!
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
We are still using Generation 1 SSDs, and they have not yet worn out!
Martin AndelSenior IT AnalystAuthor Commented:
How long are you using them for? Are they enterprise class/sas ssd's? We have the Samsung 850 Pro's.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Enterprise SSDs and we also have some Consumer ones, like 850 Pros.

We've been using them 24x7x365, for many years!
Martin AndelSenior IT AnalystAuthor Commented:
In a raid array with a card like H700?
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Yes. H700.
Martin AndelSenior IT AnalystAuthor Commented:
That is very god news! Thanks a lot for all your help!!!
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