External hard drive not showing up in ESXi Windows Server 2008 virtual machine

I've got a new 3TB external hard drive that is no longer showing up in my Windows Server 2008 virtual machine.  The VM Ware host is running ESXi 5.1.  I successfully added the hard drive last week and used it several times for the nightly backup.  Last night, the backup failed not being able to locate the folder location of the external hard drive.  I didn't make any changes to the VM settings and everything looks good.

I've tried restarting the server vm, removing the hard drive and USB controller from the VM and adding it back.  No luck

The external hard drive is simply not showing up in disk manager.

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Hypercat (Deb)Commented:
When you go to add the USB device, do you see the correct device listed?  Have you done a hard restart on the host machine?
SupermanTBAuthor Commented:
I do see the correct device listed. I have not restarted the host
Hypercat (Deb)Commented:
I hate to even mention this, but you are sure the external drive has power and is turned on, right?  I would try power cycling the external drive, and also trying a different USB Port. If that doesn't work, try if possible doing power down/power up on the host server.  It doesn't seem as though this should be necessary, but it's something to try.  Also, maybe before you try that, if you have another VM on the same host, see if you can attach the USB device to that VM.
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Zacharia KurianAdministrator- Data Center & NetworkCommented:
I would check the USB HDD by connecting to a local PC or laptop, just make sure it has no physical issues. Because it was working for you for some time. I will also make sure that the VMX version is updated + VMware tools, in your windows 2008 server.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
It's not recommended to add external USB hard drives to VMs in ESXi, USB passthrough was designed for Security Tokens or Dongles, but VMware Admins seem to think that because USB is supported you can add hard drives.

USB passthrough is very slow, for backup because the I/O is virtualised.

Check my EE Article, and then we can try some troubleshooting tips

HOW TO: Add and Connect a USB Device to a Virtual Machine, hosted on VMware vSphere Hypervisor ESX 4.1 ESXi 4.1, ESXi 5.0
SupermanTBAuthor Commented:
It appears in this case power cycling the external hard drive and then restarting the virtual machine fixed the issue.  I'm going to wait for a successful backup to run tonight before calling the all clear, but I can definitely now see the external hard drive in the server OS.
SupermanTBAuthor Commented:
This issue keeps happening.  Power cycling the the hard drive fixes it, but it's happening way too frequently.  

Any thoughts?
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
As I posted, External USB devices attached to vSphere are problematic, USB passthrough was never designed for this purpose in vSphere.

Consider Network Backups to portable NAS devices, e.g. the Western Digital World Book.
SupermanTBAuthor Commented:
I have USB passthrough working on dozens of VM servers.  While it may have never been designed for that purpose, it definitely works.

I do appreciate your recommendation on an alternate setup, but I need to solve this problem.

Do you have any thoughts on how I might be able to do that?
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
USB passthrough is problematic.

1. depends on server.

2. depends on USB chipset in server.

3. depends on make and model of USB external hard disk.

I'm afraid we do not use this or recommend as a solution for clients, because of what you have experienced.

It has been like this, since it was developed, in ESXi 4.x, and 5.x, and is no better in 5.5 U2 or future products!
SupermanTBAuthor Commented:
I do understand that you do not approve of my setup and would prefer I use a NAS configuration here.  

I however need help with this problem.  I'll be happy to provide you with the information you mentioned there if you're interested in troubleshooting this problem.

If not, I'll wait for another expert or start a new thread.  Thank you for your recommendations.
Hypercat (Deb)Commented:
I have to agree with Andrew.  I've had the same experience - some hosts have no problem with it and will work fine for years on end.  On others, I've either never been able to get it to work at all, or it doesn't work reliably.  I think it depends a great deal on the make and model of the USB drive itself.  So, if this is a different make or model from what you've used with other machines, you might try a different device. Unfortunately, these devices are constantly being "improved" by the manufacturers (that is, they're always coming out with newer models), so it may be hard to pinpoint a certain device that is consistently reliable.
SupermanTBAuthor Commented:
I definitely don't have this same exact setup on all my servers.  I do have this same exact external hard drive in use on a few VM Ware Hosts though.
SupermanTBAuthor Commented:
Additionally, with the particular VM Host in question, I've had trouble with other external hard drives.  Not just this one
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
@SupermanTB It's not that I do not approve.

It's not going to work!

USB passthrough is slow, as the I/O is virtualized, it was never designed for USB External Hard Disks, this is an error made by most VMware Admins, because they see the word USB, and think they can attach any USB device they like - wrong!,

You cannot troubleshoot an issue, if the hardware is at fault, it's not compatible, or ESXi was never designed for this purpose.

You can upload and post your /var/usb.log, but I know what the contents will be, it will not be detecting your USB external hard disk.

If not, I'll wait for another expert or start a new thread.

That is your choice....

PS This is based on our experience of using VMware vSphere for 17 years!

I'm raising a Request for Attention, so other Experts, can Assist You!

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SupermanTBAuthor Commented:
@Andrew Handcock.  I really appreciate you help and value your experience.  I have trouble with your statement that "it's not going to work" when I have several setups using the exact same hard drive where it works just fine.  No problems at all.  I do understand that the server models are different as are the chipsets in the servers.

In this particular case, everything actually works fine at times and randomly stops working.  Additionally I read articles like this where I see that USB passthrough is supported.  It's hard for me to put all this information together and come to the conclusion that it will never work.  Perhaps I'm wrong here.  I certainly don't have 17 years of VM experience.

It seems that @hypercat agrees with you.  So if other experts chime in with the same response then I'll certainly be convinced.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
randomly stops working.

that's not working correctly!

VMware did try and start creating a list of tested devices, and then stopped for USB passthrough, because it became impossible, so it's "best endeavors"

Do you have a VMware Support contract ?

What is the server hardware, I've not seen in mentioned anywhere?

What ESXi 5.1 server build are you using?

Are all the firmwares up to date on ALL servers.

Have you followed the advice in this article, and checked your Server bios USB configuration


from the above article, it states

Unsupported USB devices may not interact as expected with other ESXi/ESX features

The VMware Support "GET OUT OF JAIL CARD!"



and the VMware Supported List


Is this for a Client or your own IT Department ?

Also File and Folder backups are slow, and not efficient, and you are not taking advantage of a virtual environment, to backup your servers at block level. You are still thinking physical.

You would be well advised to re-think your Backup solution. e.g. and use a product like Veeam backup and Replication.
SupermanTBAuthor Commented:
I do not have a VMware support contract.  I haven't called them often, but in the past I believe I've done the per incident support.

Server:  Dell PowerEdge R510
Hard Drive:  http://www.amazon.com/gp/product/B00AIY9658/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
ESXi:  5.1.0, 799733

When you ask about firmwares up to date on ALL servers.  I don't want to misunderstand you.  What firmwares do you mean here?

Thanks very much.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
BIOS, Storage Controller, Network - ALL firmware on the Server.

Your ESXi build is old and out of date - update it. That's the original release GA, latest build is 2000251.

So ESXi 5.1 build is behind.

We would explore all these areas.
SupermanTBAuthor Commented:
Let me do some updating on that server and get back to you.  This particular client is very picky about bringing their server down, so it's likely going to be a week before I will be able to schedule this.

I'll let you know once I've done this.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
We would never recommend this as a client solution, they should be using a virtualisation solution. (block backup).

They need to make a decision as to what is important, no backups or a possible fix, I would be recommending a different Backup strategy.
SupermanTBAuthor Commented:
The client is using Veeam to backup to that external hard drive.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
from within the OS ?

NAS/NFS backups are quicker.
SupermanTBAuthor Commented:
there is a single virtual host running for servers. One of those servers is a utility server that uses Veeam to back up the other three servers. Currently the back up is happening to that external hard drive.
SupermanTBAuthor Commented:
Another quick question....in your opinion, backing up to NAS on a gigabit network will be faster than backing up to a USB 3.0 external hard drive?
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Correct, USB passthrough is slow, because the I/O is virtualised, and USB 3.0 devices cause even more issues!
SupermanTBAuthor Commented:
Any particular brand/model you'd recommend?
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Check the supported VMware list.

As for NAS, Synology and Western Digital Worldbooks, NetGear ReadyNAS, some now have work with Vmware stickers!
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
The device needs to support NFS or iSCSI.

Those links do not tell me.
SupermanTBAuthor Commented:
I wasn't able to find NFS or iSCSI with those products.  What about something like this?  You mentioned the Netgear ReadyNAS

Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
If it has iSCSI or NFS then yes.
SupermanTBAuthor Commented:
I installed a Synology NAS and everything is working great.  The job normally took ~20 hours to complete and with the NAS, it took ~8 hours.  

I have seen the light and have been converted.  No more USB external hard drives.
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