still doubt about iSCSI thin provisioning and allocation

foxtrotsierra

I've been trying to fully understand how iSCSI thin provisioning and allocation really works: followed several youtube videos and read several guides around and I believe it's quite clear how and when to use it. But a collegue of mine does not agree with me.

There are some Nas on the market implementing thin provisioning able to use up to 16TB of virtual size (shared amongst the iSCSI thin-provision targets).

I want to use the storage on a NAS just as a File Server connecting a windows server with the microsoft iSCSI connector to the NAS implementing thin provisioning (For example it might be a RAID1 with two HD of 500GB each).

On the NAS server let's pretend I create an iSCSI Thin-Provisioning volume using all the physical space available and I only create one target and I allocate on this target as virtual size up to the max (16 TB).

Notifications will be sent to the administrator when 90% of the physical iSCSI thin-provision volume has been utilized (400GB)

As long as I understand as soon as the hard disk would be eventually completely full (500GB) nobody would be able to access and save data on the NAS, making it unstable. Am I right? Is in this scenario impossible to exceed the 500GB limit?

Instead my colleague is firmly convinced that it's possible to exceed the 500GB limit up to the 16TB as long as the users won't access simultaneously at more than 500GB of data (Example: users opening at the same time more than 500GB of docs with a word processor etc...). Is my colleague right?!

Thanks in advance
foxtrotsierra

iBrokeIT

You can over-provision using thin provisioning giving the illusion that you have more physical resources than you actually do in reality but it is just that, an illusion. You can only actually use(write data to) the amount to have in physical resources.

I am not sure I am completely following your scenario but is your coworker basically saying you can write 16 TB of data to a 500 GB hard drive using thin provision? LOL!

darkerosxx

Your assumption is right. If you over-allocate your 500GB and reach that 500GB, your datastore will be full.

Thin provisioning is just that... It says you have X, when you really only have Y. If you reach Y, your data store is full.

foxtrotsierra

I am not sure I am completely following your scenario but is your coworker basically saying you can write 16 TB of data to a 500 GB hard drive using thin provision? LOL!

YES!!!

Thank you iBrokeIT and thank you darkerosxx. As a matter of fact, it did not make any sense what my coworker was saying.
Have a good day. Thanks

jibbajabba

iBrokeIT wrote: »

I am not sure I am completely following your scenario but is your coworker basically saying you can write 16 TB of data to a 500 GB hard drive using thin provision? LOL!

Write ? No. Allocate ? Yes

foxtrotsierra

jibbajabba wrote: »

Write ? No. Allocate ? Yes

Could you be so kind by explaining in a very simply way what allocating is?

Basically as far as I understand the windows server believes that hard disk is a 16TB unit but as soon as it exceed the physical limit (500GB) it won't allow to save other data on it. Correct?

Thanks in advance jibbajabba.

dave330i

foxtrotsierra wrote: »

Could you be so kind by explaining in a very simply way what allocating is?

Basically as far as I understand the windows server believes that hard disk is a 16TB unit but as soon as it exceed the physical limit (500GB) it won't allow to save other data on it. Correct?

Thanks in advance jibbajabba.

Allocating is assigning x amount of resources to something (usually VMs).

JeanM

dave330i wrote: »

Allocating is assigning x amount of resources to something (usually VMs).

vs. actually writing (or I should say "Storing") X amount of data.