Wanted to create VM with more than 2TB Storage

[Nilesh More1709161276]

Hi Team,

 

My Hypervisor environment is,

Xenserver Version: 8.0

Local Storage for VM storage: 10Tb (Hardware Raid)

Server: Dell R740

 

I need to create one Centos 8.3 VM and provide 5TB storage for Centos VM to store Videos.  But I realized that there is limitation of adding more than 2TB storage in single VM. Sorry but same question, Is there any other way to provide 5TB storage for single Centos 8 VM? please let me know safe and supported way.

 

Also I am thinking if 2TB is limitation then I have alternative workaround. Please let me know whether this is ok or not as performance wise. (I know there may be performance degrade)

1. Install Centos VM by allocate minimal disk storage (i.e. 100G) 100G will be only for OS data.

2. Attach 2TBx2 storage to Centos VM (i.e. /dev/xvda2 and /dev/xvda3)

3. Create software raid0 by using 2TBx2 storage which attached in step 2 (i.e. /dev/xvda2 + /dev/xvda3) and make single 4TB storage array (software raid). This will create /dev/md0 or /dev/dm0 block device with 4TB

4. Create file system on /dev/md0 and mount the same.

 

Will it work or I will get very read/write performance if I create software raid? Please suggest me 

 

Please let me know your opinion and suggest the same. I am going to host critical VM on Xenserver. So need confirmation from Xen Team.

 

Thanks,

Nilesh More

[Tobias Kreidl]

EqualLogic, NetApp, or a GFS2 based SR will support more than 2 TB, otherwise, 2 TB is the hard limit. I believe you require an Enterprise version of Citrix Hypervisor to get GFS2 support.

 

-=Tobias

 

 

[Alan Lantz]

Completely unsupported if it does work. The bigger problem is backing up and restoring large data sets like that

within XenServer. I cap my VM's at 300GB. Anything larger than that I move data out to SAN/NAS.

 

--Alan--

 

[Nilesh More1709161276]

36 minutes ago, Tobias Kreidl said:

EqualLogic, NetApp, or a GFS2 based SR will support more than 2 TB, otherwise, 2 TB is the hard limit. I believe you require an Enterprise version of Citrix Hypervisor to get GFS2 support.

 

-=Tobias

 

Thanks Tobias for your quick response. What else if i create software raid by using 2x 2TB VDI? Please suggest.

 

[Nilesh More1709161276]

18 minutes ago, Alan Lantz said:

Completely unsupported if it does work. The bigger problem is backing up and restoring large data sets like that

within XenServer. I cap my VM's at 300GB. Anything larger than that I move data out to SAN/NAS.

 

--Alan--

 

Thanks Alan for your quick response. There is work-around. can you check-https://medium.com/shehuawwal/how-to-create-or-add-more-than-2tb-storage-to-xen-server-xcp-ng-virtual-machine-vm-eaf8042f06c6 

I know this is not official statement but if its work for me then please suggest.

[Tobias Kreidl]

XenServer/Citrix Hypervisor does not support software RAID. You can also consider running XCP-NG, instead, which does support software RAID and use also that workaround you referred to above. I still think GFS2 is your best bet. Doing a software RAID on the VDI level probably won't work at all. And to Alan's point, a backup/restore of huge storage devices becomes very iffy once they get closer to 1 TB or above. I can't recall if the timeout is stilla t 24 hours or in newer versions was upped to 48 hours, but at some point, and export or import will simply time out.

 

-=Tobias

[Alan Lantz]

Incremental backups can be a solution, it depends on the type of data you are backing up. 

That link that you showed expanding LV Storage, very interesting. I personally always tried

to never do things like that in production.  So I would say if your comfortable with Linux

and running unsupported and your backup scheme is solid go for it. 

 

--Alan--

 

 

[Tobias Kreidl]

I've had some bad experiences (along with some successes) the few times I've worked on expanding LVM, even on stock Linux boxes. Not something for the faint of heart. LVM can be like a house of cards when you start mucking around with the internals.

[Mark Syms]

Raiding/striping disks inside the VM is the only option apart from GFS2 to get more than 2TB as a single device inside the VM. Citrix won't raise any red flags as what you do inside your VM is none of our business.

[Mark Syms]

We don't support software raid in the Hypervisor Dom0 but that has nothing to do with software raid in the guest VM.