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amediratta
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June 28th, 2009 08:00
Disk Space Lost
We had asked to configure a few LUNs on our Clariion box using a total of around 4.5 TB of 11 TB usable capacity available. This was done and working fine.
We now want to use the balance 6 TB as 3 LUNs of 2 TB each but we are told that we can get 2 LUNs of 2 TB, one for 940 GB & around 8 more LUNs of smaller capacities ranging from 98 GB to 220 GB. We are asked to use them individually.
The application requirement is a large LUN. We have been told that these small LUNs cannot be combined and have to be used like this. Since our application does not work on small LUNs, we would need to upgrade and buy more disks and actually are losing around 840 GB in these small LUNs.
Is there a way by which we can combine them? Also, what is it that makes us loose space when we create LUNs? These are small spaces but they amount to something like 840 GB i.e. around 8 % of our requirement.
Please suggest.
We now want to use the balance 6 TB as 3 LUNs of 2 TB each but we are told that we can get 2 LUNs of 2 TB, one for 940 GB & around 8 more LUNs of smaller capacities ranging from 98 GB to 220 GB. We are asked to use them individually.
The application requirement is a large LUN. We have been told that these small LUNs cannot be combined and have to be used like this. Since our application does not work on small LUNs, we would need to upgrade and buy more disks and actually are losing around 840 GB in these small LUNs.
Is there a way by which we can combine them? Also, what is it that makes us loose space when we create LUNs? These are small spaces but they amount to something like 840 GB i.e. around 8 % of our requirement.
Please suggest.
RobertDudley
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Posted June 29th, 2009 05:00
By losing space do you mean losing space in the lun or on the clariion. The lost space can likely be the protection for the lun. For instance if you create a 500GB usable lun on a raid 5 (4+1) disk setup you will take up an additional 25% more space in the raid group building out the parity protection. That 500 GB usable lun actually takes up 625 GB of space in the raid group.
Message was edited by:
RobertDudley
Message was edited by:
RobertDudley- One of the first things you need to do is to run a report on the array to get a list of all the Raid Groups and the amount of free space and the amount of free CONTIGUOUS space. It's the free contiguous space that is most important. This is what is used to create LUNs.
Once you have the list of where all the free space and free contiguous space is located, then you should be able to start planning where you can create LUNs and what the sizes of the LUNs can be.
glen
dynamox
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Posted June 28th, 2009 17:00