SAN LUNs Do Not Act Like NAS Shares
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@ntoxicator said:
Would it be better for me to pass my iSCSI LUN directly to Windows Server and use the Windows iSCSI initiator? Or is it just bad... And would be better leaving Xen Server handle the entire ISCSI LUN?
That's just bad. Don't even consider that a possibility. This should always be handled by the hypervisor for all intents and purposes.
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@ntoxicator said:
However, then I thought.... it would be WAY easier to just attach an iSCSI volume directly to Windows using the Initiator. Then I can simply Grow the iSCSI LUN through my Synology NAS and be done...
What would make this easier? Using iSCSI at all and using guests VM access to it should never be easier. I'm missing something here. How would that happen?
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@ntoxicator said:
So what is conscious here?
Would it be better for me to pass my iSCSI LUN directly to Windows Server and use the Windows iSCSI initiator? Or is it just bad... And would be better leaving Xen Server handle the entire ISCSI LUN?
As right now, I have total of two(2) iSCSI LUN's attached to Citrix Xen Server and the node.
One LUN #1, I have a disk I created which is attached to my Windows Server 2008 R2 Domain Controller. This disk is nearly 1TB in size and almost full.
I've been wanting to Attach a new storage Repository (NFS) to Citrix Xen Server... And then MIGRATE the ENTIRE 1TB disk to this NFS volume as it would be much larger and easier to manage the raw disk file.
However, then I thought.... it would be WAY easier to just attach an iSCSI volume directly to Windows using the Initiator. Then I can simply Grow the iSCSI LUN through my Synology NAS and be done...
Never* pass raw storage to your VMs, it defeats several advantages to virtualization without adding anything of value. Plus the Windows iSCSI implementation is really not good you would be introducing a lot of issues.
*Of course there are times when you may want to do this but they are few and far between.
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Thank you sir!
I was just trying to make it simple at the possibility of less overhead to achieve better throughput on 1GBe network.
Any reason why Windows doesnt see the growth in the disk when I expand it at hypervisor level? Will this still happen when moving to NFS Storage Repository?
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@ntoxicator said:
However, I've had issues with Windows Server. Every time I've expanded the disk within Citrix Xen Server.... Windows server see's the new growth as a separate drive and I have to use software to merge the partition sizes together.
This has nothing to do with XenServer (it's always XenServer, never Xen Server. The space matters, there are XenServer and Xen server and they mean different things.) This is purely about how Windows deals with growing block storage. Using iSCSI will be identical. Your issues around automatic resizing are purely inside of Windows, XenServer has no influence or control here.
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@ntoxicator said:
I was just trying to make it simple at the possibility of less overhead to achieve better throughput on 1GBe network.
The network bottleneck remains identical either way. It's system overhead alone that varies and is very close to equal as each is more efficient at a different stage of the process. But one gives full visibility and control, one breaks the virtualization model unnecessarily.
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Thank you again Scott!
Now... what you think would be more reliable or simpler solution?
Use XenServer to migrate(move) the disk to the new Storage Repository (NFS)? This will take several hours.. And I'm worried that if something fails the entire disk migration will be lost.. or will XenServer do block by block and if any fail, it will keep on the original SR?
Or should I just attach a new disk to the Windows Server VM (From the NFS Storage Repository) and manually copy all the files over using Microsofts data copy utility.. so the share folders & file permissions are carried over
As I'll need the keep the same drive letter
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@ntoxicator said:
Thank you again Scott!
Now... what you think would be more reliable or simpler solution?
Use XenServer to migrate(move) the disk to the new Storage Repository (NFS)? This will take several hours.. And I'm worried that if something fails the entire disk migration will be lost.. or will XenServer do block by block and if any fail, it will keep on the original SR?
Or should I just attach a new disk to the Windows Server VM (From the NFS Storage Repository) and manually copy all the files over using Microsofts data copy utility.. so the share folders & file permissions are carried over
As I'll need the keep the same drive letter
Are you currently not doing backups of this system? While losing the data is an understandable concern that risk should be tempered by having an offline copy of it somewhere.
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The windows DC is backed up to Carbonite.
I am backing up the LUN's on the Synology Rackstation a remote disk.
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@ntoxicator said:
The windows DC is backed up to Carbonite.
I am backing up the LUN's on the Synology Rackstation a remote disk.
Could you restore from that backup to the NFS storage and then add that to Windows? Still would have a potential network bottleneck and would still require downtime but you wouldn't be as concerned about data dropping.
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I probably could pull down the backup from carbonite as its backing up the entire data partition. However, then comes the restore time.
The Synology LUN backup is just LUN. cannot export to NFS. So would have to use Carbonite to restore.
I suppose all the options have their issues. no clean cut solution
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Why does the XenMotion approach not work?
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I have no experience with XenMotion?
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@ntoxicator said:
I have no experience with XenMotion?
That's realistically the only tool to be looking at here. It will "just do what you want." It will move the storage over, while everything is running, without downtime or extra tools.
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XenMotion is paid product / support. Again right now we're using XenServer Free edition.
Great it can move the storage disk over while its running. However, users are constantly writing data to it as its an SMB Share from Windows Domain controller
Folders are on this drive "data disk" and windows domain controller handles the folder shares & file permissions.
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@ntoxicator said:
XenMotion is paid product / support. Again right now we're using XenServer Free edition.
XenMotion is available in XenServer... I can do it in my home lab without any issues.
Check out the wiki link I posted earlier.
https://wiki.xenserver.org/index.php?title=Storage_XenMotion
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@ntoxicator said:
Great it can move the storage disk over while its running. However, users are constantly writing data to it as its an SMB Share from Windows Domain controller
Folders are on this drive "data disk" and windows domain controller handles the folder shares & file permissions.
That's the point... it was literally designed for this.
It writes all new changes to the new location and merges the unchanged data into the new location. You won't risk downtime or losing writes with this technology.
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@ntoxicator said:
XenMotion is paid product / support. Again right now we're using XenServer Free edition.
I know nothing of the non-free version. I would never buy that or recommend a paid version. XenMotion is free.
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@ntoxicator said:
Great it can move the storage disk over while its running. However, users are constantly writing data to it as its an SMB Share from Windows Domain controller
That is exactly what XenMotion is for. If users were not writing to it, you would have no need for XenMotion, you could just copy.
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Thank you. I will look into it?? As Within XenCenter, I click the XenServer node and the disk attached and when I click "move" it throws me an error.
however, when the VM is shut down - i can move the disk without problem..
Its just concerning that its a Windows Server domain, with shares. How would it still be able to write the data to the new Storage Repository and put it back together and be fine? meh