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MSA2000 LUN size diference from Host LUN size

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Fernando Boza
Regular Advisor

MSA2000 LUN size diference from Host LUN size

El tamaño de una LUN en una MSA2000 es muy diferente al tamaño observado en el host. Alguien me puede dar una explicación al respecto?
6 REPLIES
RASHMI
Trusted Contributor

Re: MSA2000 LUN size diference from Host LUN size

Hi Fernando,
Thanks for using HP forums!
Could you please converse in English? This will help everybody in the Forum understand the discussion and allow them to participate as well.
Thanks & Regards,
Rashmi
Thanks,
Rashmi
Forum Moderator
Steven Clementi
Honored Contributor

Re: MSA2000 LUN size diference from Host LUN size

How much different are we talking? I usually see a little discrepency with the size from the array to the host.. and on the MSA, it seems to be a little larger than normal, but how much of a difference are you talking about?


Steven


Don;t fault me... fault Google...

(¿Cuánto diferentes estamos hablando? Yo suelo ver un poco de discrepancia con el tamaño de la matriz con el host .. y en la MSA, que parece ser un poco más grande de lo normal, pero ¿cuánto de una diferencia estás hablando?)
Steven Clementi
HP Master ASE, Storage and Clustering
MCSE (NT 4.0, W2K, W2K3)
VCP (ESX2, Vi3, vSphere4, vSphere5)
RHCE
NPP3 (Nutanix Platform Professional)
Fernando Boza
Regular Advisor

Re: MSA2000 LUN size diference from Host LUN size

the difference is significant.... 2GB in MSA ~ 1,6GB in host
Sivaramakrishna_1
Honored Contributor
Solution

Re: MSA2000 LUN size diference from Host LUN size

Hi,

Its simple Logic. I referred some documents long back(could not able to trace now), MSA will be taken as Size in 1000 KBytes=1MB instead of 1024 KBytes =1 MB.

This resulting the less size LUN when compared with created size.

Below is one of the Informative advisory fyi.

Information
A volume created in MSA Console does not show up as the same size in Operating system.
For e.g. If a Volume in MSA created is 700GB, in Operating system it would show as 652GB volume.
Details
In the MSA console, the size defined is with a decimal (base 10). Which means, if size specified is 1000MB it is taken as 1GB.
However the file system at the OS Data capacity is calculated in binary (base 2).
Capacity comparison:
Unit MSA Data Capacity File system Data Capacity
Kbyte (KB) 1000 bytes 1024 bytes
Mbyte (MB) 1 million bytes 1,048,576 bytes
Gbyte (GB) 1 billion bytes 1,073,741,824 bytes
Tbyte (TB) 1 trillion bytes 1,099,511,627,776 bytes
Taking the above example.
700GB (in MSA) = 700,000,000,000 bytes
652GB (in OS) = 667,648 MB = 683,671,552 KB = 700,079,669,248 bytes
Steven Clementi
Honored Contributor

Re: MSA2000 LUN size diference from Host LUN size

Yea, but that doesn't explain why there is an additional 260MB missing.

2GB would be about 1.86GB in th OS.


The only thing left to consider is that the "RAID" level is not applied to the array, rather the volume.

I've had to compensate for this in the pasted to get the sizes I wanted in the OS. Never had to re-visit it though... an I do;t have a MSA handy to do so now.


How many disks are configured in the disk group and what is the RAID setting?


Losing an additional 10 to 15% off the top sounds like RAID5.


Steven
Steven Clementi
HP Master ASE, Storage and Clustering
MCSE (NT 4.0, W2K, W2K3)
VCP (ESX2, Vi3, vSphere4, vSphere5)
RHCE
NPP3 (Nutanix Platform Professional)
Sivaramakrishna_1
Honored Contributor

Re: MSA2000 LUN size diference from Host LUN size

We need to consider that 1.86 GB space is of Disk capacity visible under OS or is it the free space after Formatting the Volume.

If it is the space after formact then we need to consoder the overhead due to formatting the volume..