Solved Get Large Disk Images on XenServer 6.5 on Local Filesystem?
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Using local storage to host the XenServer SR, there is a natural 2TB limit on disk image sizes. What is the best method for bypassing this limitation currently?
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There isn't one that I'm aware of. It's better to have multiple small disks for recovery purposes anyways. (small 2TB)
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Only useful for recovery if the storage is broken up. Otherwise it actually makes recovery harder and more problematic.
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See here for a reply from Tobias.
"For larger storage, we attach directly from the VM via either iSCSI or NFS and bypass the whole SR mechanism altogether (which has both plus and minus points)."
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@DustinB3403 That won't help in the case of local storage, correct?
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From what his reply is no, it would have to be external.
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What about StarWinds?
OK now that I wrote that, maybe not. Am I right that StarWinds is a VM in the hypervisor? So it would be in the SR, right?
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@Dashrender said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
What about StarWinds?
OK now that I wrote that, maybe not. Am I right that StarWinds is a VM in the hypervisor? So it would be in the SR, right?
That's correct. It would have to deal with getting data in 2TB chunks too.
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@DustinB3403 said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
See here for a reply from Tobias.
"For larger storage, we attach directly from the VM via either iSCSI or NFS and bypass the whole SR mechanism altogether (which has both plus and minus points)."
I thought that NFS maintained the limitation because it has the same file type that local does. As would SAN.
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@scottalanmiller I believe what they are doing is creating a small (2TB-4GB) partition at most, and then inside of the VM it's self attaching an ISCSI device to be another disk.
One that Xen doesn't even know about.
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@DustinB3403 said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
@scottalanmiller I believe what they are doing is creating a small (2TB-4GB) partition at most, and then inside of the VM it's self attaching an ISCSI device to be another disk.
One that Xen doesn't even know about.
Yeah, that's just silly. There has to be a better solution. LVM spanning will do it, but.... talk about a 2007 approach.
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So while driving and quickly reading through this, I found this. https://community.spiceworks.com/topic/394390-citrix-xenserver-6-2-local-storage-2tb-limit
Looks like changing to GUID might allow more space.
If u misunderstood what you were saying, sorry I'm driving.
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@johnhooks said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
So while driving and quickly reading through this, I found this. https://community.spiceworks.com/topic/394390-citrix-xenserver-6-2-local-storage-2tb-limit
Looks like changing to GUID might allow more space.
If u misunderstood what you were saying, sorry I'm driving.
The limitation is not the size of the SR but the size of the VHDs that you can create on top of it.
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@scottalanmiller said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
@johnhooks said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
So while driving and quickly reading through this, I found this. https://community.spiceworks.com/topic/394390-citrix-xenserver-6-2-local-storage-2tb-limit
Looks like changing to GUID might allow more space.
If u misunderstood what you were saying, sorry I'm driving.
The limitation is not the size of the SR but the size of the VHDs that you can create on top of it.
Ah ok. This person says it's because of a limit on Microsofts VHD format. https://joetutorials.wordpress.com/2015/06/03/how-to-create-virtual-disks-greater-than-2gb-in-xenserver/
Is there any way to use a raw LV instead of a VHD?
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@johnhooks said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
@scottalanmiller said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
@johnhooks said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
So while driving and quickly reading through this, I found this. https://community.spiceworks.com/topic/394390-citrix-xenserver-6-2-local-storage-2tb-limit
Looks like changing to GUID might allow more space.
If u misunderstood what you were saying, sorry I'm driving.
The limitation is not the size of the SR but the size of the VHDs that you can create on top of it.
Ah ok. This person says it's because of a limit on Microsofts VHD format. https://joetutorials.wordpress.com/2015/06/03/how-to-create-virtual-disks-greater-than-2gb-in-xenserver/
Is there any way to use a raw LV instead of a VHD?
Yes, you can bypass the VHD format. But that's a crappy approach. Getting XS to create a VHDX would be so much better.
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@scottalanmiller said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
@johnhooks said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
@scottalanmiller said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
@johnhooks said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
So while driving and quickly reading through this, I found this. https://community.spiceworks.com/topic/394390-citrix-xenserver-6-2-local-storage-2tb-limit
Looks like changing to GUID might allow more space.
If u misunderstood what you were saying, sorry I'm driving.
The limitation is not the size of the SR but the size of the VHDs that you can create on top of it.
Ah ok. This person says it's because of a limit on Microsofts VHD format. https://joetutorials.wordpress.com/2015/06/03/how-to-create-virtual-disks-greater-than-2gb-in-xenserver/
Is there any way to use a raw LV instead of a VHD?
Yes, you can bypass the VHD format. But that's a crappy approach. Getting XS to create a VHDX would be so much better.
Agreed. If you need to have it though, you could get the same functions with LVM, just would take some manual work.
But that sucks. I wonder why they chose VHD vs something like qcow2 which has a limit of like 9 million TBs.
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@johnhooks said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
@scottalanmiller said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
@johnhooks said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
@scottalanmiller said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
@johnhooks said in Get Large Disk Images on XenServer 6.5 on Local Filesystem?:
So while driving and quickly reading through this, I found this. https://community.spiceworks.com/topic/394390-citrix-xenserver-6-2-local-storage-2tb-limit
Looks like changing to GUID might allow more space.
If u misunderstood what you were saying, sorry I'm driving.
The limitation is not the size of the SR but the size of the VHDs that you can create on top of it.
Ah ok. This person says it's because of a limit on Microsofts VHD format. https://joetutorials.wordpress.com/2015/06/03/how-to-create-virtual-disks-greater-than-2gb-in-xenserver/
Is there any way to use a raw LV instead of a VHD?
Yes, you can bypass the VHD format. But that's a crappy approach. Getting XS to create a VHDX would be so much better.
Agreed. If you need to have it though, you could get the same functions with LVM, just would take some manual work.
But that sucks. I wonder why they chose VHD vs something like qcow2 which has a limit of like 9 million TBs.
I wonder that too, since Xen supports it. It is an XS limitation, not an Xen one.
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@scottalanmiller Here's a recent discussion from the Citrix forums that addresses this topic.
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@This - driving me crazy!. As we're looking to move to localized server/storage and AWAY from a NAS setup external storage.
So, attach 2TB disk to the Virtual Machine within XenServer. its 2TB limit due to Microsoft VHD limitations....
So, say we're attaching this 2TB disk to a Windows Server VM..... be limited as far as storage needs go. In our usage case, this would be for Employee profiles / save data. I see this being an issue in the long run.
Only way around, would be to setup a NFS share or SMB share and attach it as a network drive to the Guest Operating system and or GPO policy to map this network share to employee's to save data.
Then you're still including a network level SAN/external storage.... which is single point of failure.
@scottalanmiller always beats us up on having SAN/External storage. Unless ofcourse has split controllers / arrays for redundancy. I would love to have me a EMC VNXe..
EDIT: beats us up over the fact of single point of failure, or more than one point of failure by introducing server + external network storage. As if network storage device goes down, lose your Storage Repository.
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@ntoxicator The issue here (does present a single point of failure) but only for the storage device.
Sure if that device dies that storage is offline, but the VM is still usable. So it's a Storage SPOF, rather than a System SPOF.
I'd rather have a Storage SPOF (in this case) than a System SPOF if I had the choice. Which to alleviate this SPOF you'd get a good NAS/SAN and use that.
Not a unreliable piece of garbage.
