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RNAR
Enthusiast
Enthusiast

one datastore can't see available LUNs for extention

I have multiple datastores and multiple available LUNs. With all but one datastore, I click the increase... button and get 3 LUNs available to be added as an extent. But with one of the datastores, the list is empty. That datastore already has 8 extents. I have extended it before.

Any ideas why the LUNs do not show up? I've read other articles on this and they usually say something like, rescan or focus on the LUN. But, it's not the host nor LUN that is having the problem as you can see, it is specifically this datastore.

vSphere 5.5 (fully patched, I think)

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continuum
Immortal
Immortal

>> That datastore already has 8 extents. I have extended it before.
Wow I was not aware that ESXi ever allowed such an insanely high number of extents.
I hope that the current versions have been fixed and do not allow more then 3 extents.
If I had to decide on that question I would suggest to not allow extents at all !!!

Are you aware of the problems you will run into if just one of those 8 extents fails ?

I highly recommend that you reconsider your plan to add another extent !!!

 

Ulli


________________________________________________
Do you need support with a VMFS recovery problem ? - send a message via skype "sanbarrow"
I do not support Workstation 16 at this time ...

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RNAR
Enthusiast
Enthusiast

According to the documentation, one should be able to add 32 extents. And I understand that if the first extent is lost, then the entire datastore will be lost. If other extents are lost, then I gather that one will only lose the virtual disks that at least partially reside on that extent, thus not really different from having a separate datastore. I am indeed relying on the fault tolerance of the storage area network subsystem and backups.

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continuum
Immortal
Immortal

> I am indeed relying on the fault tolerance of the storage area network subsystem and backups.

So you replicate your SAN to a second SAN daily and have daily backups of all your VMs ?

Anyway - from my experience with VMware related recoveries I learned that if you lost one extent the whole datastore can no longer be mounted at all.
It will tell you something like: datastore is unmountable due to one or more extents are missing.
So the loss of one extent is not a minor and harmless incident - it usually means that all VMs stored on that datastore will not be available in production for at least one or two days.
Most vsphere admins will not be able to deal with such a desaster. VMware support will not help either as such an issue is regarded as a recovery case and VMware support does not help with recoveries.
Even if the lost extent is still available fixing this problem is something that is completely undocumented and when it happens I think most users either give up after a few days or consult companies like Kroll Ontrack.

I had success a few times with datastores using one or two extents - if you asked me to fix an 8 extents datastore my first response would be : oh dear ... oh dear ...

I hope you are using this 8 extents datastore in a hobby lab with discardable data and dont use it in production.
If you are using this in production I must tell you that you are running an unacceptable risk and that you MUST start to rebuild your environment right now.

Ok - this does not help you at all right now. I you are  a true warrior-admin and still want to add one more extent I may have a couple of suggestions.
But please provide some details first.

I would like to see a dump of the first 30 mbs of the affected datastore.

To create such a dump run a command like
dd if=/dev/disks/naa.*****:* bs=1M count=30 of=/tmp/8-extents-header.bin

replace naa****:* with the details of your datastore.

Ulli

 

 

 


________________________________________________
Do you need support with a VMFS recovery problem ? - send a message via skype "sanbarrow"
I do not support Workstation 16 at this time ...

RNAR
Enthusiast
Enthusiast

I don't actually know much about this and did not setup this system. I think I have been convinced to just add another datastore. It is unfortunate because that has the problem of wasting space as one needs to leave a certain amount of space available on every datastore for snapshots and issues like that. But anyway, I'll try to get that data because I'm still at least curious as to why it isn't working as it seems that it should.

 

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scott28tt
VMware Employee
VMware Employee

@RNAR 

If you are running anything like production workloads you should consider upgrading to at least 6.5, only that version and later are still supported and updated.

 


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RNAR
Enthusiast
Enthusiast

I just realized, I'm probably not permitted to share the contents of that 30MiB of storage. And besides, I can't seem to find the file created. So, I'll just call this unanswerable and go another way.

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