Physical Disk Size in the RAID utility

Question

Hi,

I just purcahsed a Dell Power edge 620 and am in the process of configuring the RAID virtual disks. I noticed that even before I configure the RAID type the physical disk sizes shown by the RAID utility is less than the actual disk size. Why would this be?

For example all 146GB disk shows at 136.12GB and all 300GB disk showing as 278.7GB

I have only ever configured HP servers and they always showed the exact same physical disk size as the acutal disk size.

Here is my configuration:

2x 146GB disk configured for RAID 1

10x 300GB disks configured for RAID 5

RAID controller PERC H710P Adapter Bios configuration utility 4.03-0002

does nayone know why this would be? is it s setting?

theflash1932 · Accepted Answer

This is normal ... explanation:http://www.dslreports.com/faq/9716 If HP shows you the full size, then they do like Apple does and shows you the binary size.  Windows and some other OS's and devices (Dell's tools, and even some Linux distros) will show you the size in decimal. You might think you are getting the full 300GB when presented in binary, but the thing you need to remember is that a file will take up more binary space than decimal, for the same reason, filling up your storage faster.  Whether you are presented the storage in binary or are seeing the actual usable storage, you will only ever get (x)binary = (.93x)decimal for storage.

CiaranM · Answer

Great thank you for the answer

AvocadoAnimalHo · Answer

Hi, This is the common issue with disk drive manufacturers advertising disk sizes in decimal bytes versus using binary bytes which computers normally use to represent sizes. An advertised 1TB disk (1,000,000,000,000 bytes) is actually about 931GB or 0.909TB in binary bytes. I.e. 931 * 1024 * 1024 * 1024 = 999,653,638,144. Most drive size utilities in OSs and RAID utilities calculate KB, MB, GB, TB, PB using binary bytes. Years ago were one or two drive manufacturers which used binary bytes but probably since all the others used decimal bytes, their same sized disk drives seemed smaller. I believe all now use decimal bytes. Here's a simple web article on this: http://usefulglyphs.wordpress.com/2009/11/11/why-actual-hard-disk-space-does-not-match-the-size-indicated-on-the-drive/ I spent a few minutes to find one with more of the real history behind disk drive sizes, but couldn't find it right now. Cheers, Stefan Steiner

PowerEdge HDD/SCSI/RAID

Physical Disk Size in the RAID utility

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