Differences between Disk Size & Capacity On Exadata Disks

Asset ID:	1-71-1950629.1
Update Date:	2014-12-10
Keywords:

Solution Type Technical Instruction Sure

Solution 1950629.1 : Differences between Disk Size & Capacity On Exadata Disks

Applies to:

Exadata X4-2 Hardware - Version All Versions and later
Oracle Exadata Hardware - Version 11.2.0.2 and later
Information in this document applies to any platform.

Goal

Explain the difference between manufacturer's reported disk size and what we actually report vi CELLCLI etc

Solution

Example:

This is just a case of units being reported, fdisk shows 3999999721472

And manufacturers claim this is 4TB whereas it is actually 3.64TB raw size disk capacity.

Because they divide down using K=1000 bytes

M 1000*1000
G=1000*1000*1000
T=1000*1000*1000*1000

This is industry convention in advertised disk sizes.

Whereas cellcli uses the proper definition where

K=1024
M=1024*1024
G=1024*1024*1024
T=1024*1024*1024*1024

So cellcli is reporting in real GB useable formatted disk space.

Now a GB is bytes/(1024*1024*1024)

So we have

3999999721472/(1024*1024*1024)

3999999721472 Bytes=3725.2900390625 GB

as displayed showing actual useable disk capacity for the lun.

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