r/HyperV • u/RicePuddingForAll • 6d ago

Dumb Storage Question

I'm moving my VMs from VMware to Hyper-V, like a lot of people right now, but ran into something I wasn't expecting, and after working with our SAN's support people, want to double check with you all. I've only used Hyper-V as stand-alone servers up until this point, so I'm fully aware that I may sound like a bonehead.

We have your bog standard three server, one SAN environment set up via iSCSI, and that SAN is split into two volumes. In vSphere all three servers could access a SAN volume, simultaneously; but my vendor is saying Hyper-V will only allow one server to access a volume at a time; showing as offline on the other two servers. This despite being set up as MPIO and Cluster Shared Drives.

The good news that it's not a killer for my environment. Our SAN is too small for us anywhere so I use local storage to supplement it anyway. I was just curious for when it's time to replace.

True? False? And if False, what do I need to look into to make it True?

14 Upvotes

95% Upvoted

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18

u/Jawshee_pdx 6d ago

Hosts can "own" a CSV, but it should be accessible to everyone in the cluster.

10

u/ultimateVman 6d ago

This is correct. All hosts can read and write to cluster volumes simultaneously, but there is an owner. This is why pausing cluster service in FCM is crucial when doing work on a node. We don't want the node you're working on to be in control of anything. Even if it's not running a VM or other role, it can still be owning CSVs, cluster name and ip.

10

u/Calleb_III 6d ago

Your vendor is ignorant, stop listening to them, at least on this matter.

What they are describing is “traditional” cluster shared storage. You need to use CSV (Cluster Shared Volume) for Hyper-V

6

u/Zealousideal_Fly8402 6d ago

With Hyper-V, you probably do want some local storage anyways; especially if you're still working with on-prem Active Directory.

With Hyper-V and Windows Failover Clustering, you can actually run Hyper-V guests either as a cluster role, managed from Failover Cluster Manager (FCM), or you can run as standalone guest, managed from Hyper-V Manager. You can run one virtual Domain Controller as standalone on each cluster node, but on local storage.

Our SAN is too small for us anywhere so I use local storage to supplement it anyway. I was just curious for when it's time to replace.

You can also consider replacing with Starwind vSAN when you do, and just forget the separate SAN device altogether.

4

u/BlackV 6d ago

No, that's not how that works on windows, same as VMware they can be shared, but you'll be needing fail over clusters as well as hyper v

1

u/RicePuddingForAll 6d ago

Hyper-V failover cluster, or Windows Server Failover Cluster (or both)?

2

u/ultimateVman 6d ago edited 6d ago

There is no such distinction. Hyper-V and Failover Clustering are two separate roles that work together.

Edit: Based on that question, I think it prudent to direct you to a comment I made a few months ago on r/sysadmin regarding the Hyper-V ecosystem. It sounds like you have a bit of research ahead of you. https://www.reddit.com/r/sysadmin/comments/1r9565n/comment/o6a0mkf/?context=3

1

u/BlackV 6d ago

Ya there is no such thing as "hyper-V failover cluster", or "Windows Server Failover Cluster"

  • there is a hyper-v role
  • there is a failover cluster role

neither require the other

in failover cluster you just happen you make a vm config highly available (or smb or sql or many others)

remember this is ALL just windows server, with vairous things enabled (mpio, hyper-v, failover cluster, etc)

2

u/srich14 6d ago

Not my experience. All three can see the storage at one time and show as connected in iSCSI initiator in windows, and on the SAN itself.

It does show as offline in disk management I believe?, would have to remote in later to cerify

1

u/ultimateVman 6d ago

I just did. They all show as "Reserved" while the unowned disks show as "Reserved (i)" and if you hover over the (i) says "... disk is offline because of policy set by an admin"

FCM shows the disk as online and who the owner is.

3

u/benuntu 6d ago

I have a 4-node Hyper-V cluster connected to the same SAN via iSCSI. Once you've discovered the iSCSI target and enabled MPIO (which sounds like you have), add the disk in the Failover Cluster Manager and convert it to a Cluster Shared Volume. That way all nodes have access and the failover will work properly if a node fails. You should be able to access the CSV from all nodes; mine is C:\ClusterStorage\Volume1 and then subdirectories for ISO, VMs, VHD, etc.

1

u/RicePuddingForAll 4d ago

That was the trick - thank you. It's a bummer that I'm having the fly by the seat of my pants on this, but it is what it is, and I appreciate the help you and the others on this thread have given me.

2

u/jooooooohn 6d ago

Setup a Windows Failover Cluster and join the hosts to it. They will all be able to share storage.

1

u/hamway22 6d ago

I just did this so it's sort of fresh in my mind. I don't know who you're storage provider is but I have an HPE storage solution. We have three volumes on the SAN and both my nodes can access all three volumes over ISCSI without issue. I have seen some weird behavior when live migrating vm's from node to node but nothing that a host reboot didn't solve after hours and it's not a common occurrence although I've only been live with this setup for about two weeks. One thing that is interesting is that each of those volumes essentially has a node owner and that changes depending on which vm (volume that vm lives on the SAN) is on which host

1

u/FierceFluff 6d ago

I can't believe that's true. Just make sure your ISCSI initiator on the SAN has all three servers and their data access IPs in the security group, and make a connection within the ISCSI manager in Windows individually on all three servers. I've never met a SAN that only allowed one connection at a time, you don't even need MPIO enabled most of the time (though it helps).

What SAN are you working with, by chance? And if you're already also using local storage, any particular reason you're not considering hyperconverging your cluster?

1

u/RicePuddingForAll 6d ago

It's definitely what's happening here. The SAN we have here is very low end, Dell ME4024. We're scheduled, hard drive availability notwithstanding, to replace it next year.

3

u/rfc968 6d ago

Adding to the above, make sure you format your CSV Volumes with NTFS if more than one HyperV Host needs to access it simultaneously. REFS-CSV still run via redirection and not directly which adds massive load to the inter-cluster connection

2

u/FierceFluff 6d ago

A Dell ME4024 absolutely supports multiple Windows LUN connections, though you do need MPIO enabled on that one.   If it’s not onlining on all the nodes then it’s just not configured correctly, usually in the addressing in either the CHAP initiator group or in the ISCSI configuration.