Home > Ask the Storage Technology Experts > Questions & Answers > Calculating available disk space in a RAID-5 set
Ask The Storage Expert: Questions & Answers
EMAIL THIS

Calculating available disk space in a RAID-5 set

Stephen Foskett EXPERT RESPONSE FROM: Stephen Foskett

Pose a Question
Other Storage Categories
Meet all Storage Experts
Become an Expert for this site
>
QUESTION POSED ON: 09 December 2004
I'm trying to find out how to calculate how much disk space will be available from five 36 GB disks using RAID-5. Can you help me out?


Digg This!    StumbleUpon Toolbar StumbleUpon    Bookmark with Delicious Del.icio.us   



RELATED RESOURCES
2020software.com, trial software downloads for accounting software, ERP software, CRM software and business software systems
Search Bitpipe.com for the latest white papers and business webcasts
Whatis.com, the online computer dictionary


There are two parts to this question. First, you need to calculate the usable space on each disk, which, surprisingly, is NOT 36 GB! Disk vendors define a gigabyte as one billion bytes, but operating systems normally define it as 2^30 (1,073,741,824) bytes. So your 36 GB disks really hold just over 33 GB of files.

Next, you need to calculate the overhead of your RAID set. A RAID-5 set of N disks leaves N-1 times the space of each disk for storage. So your five disk set has the space of four disks, or 134 GB. Remember, too, that filesystems and volume managers have some overhead. Expect to use about 130 GB on your RAID set.

Read other answers to this question:

  • How to calculate available disk space on a RAID 5 answered by Ashley D'Costa
  • Calculating available disk space in a RAID-5 set answered by Brett Cooper

    		•



    Search and Browse the Expert Answer Center
    Search and browse more than 25,000 question and answer pairs from more than 250 TechTarget industry experts.
    Browse our Expert Advice



    Search for Data Management Tools
    TechTarget Storage Media
    Storage Magazine View this month\\'s issue and subscribe today.
    Storage Decisions Apply online for free conference admission.
    		SearchStorage.com
    HomeNewsMagazineTopicsLearningMultimediaWhite PapersBlogsEventsAbout Us
    SEARCH :     Site Index Powered by: Search Powered by Google

    About Us  |  Contact Us  |  For Advertisers  |  For Business Partners  |  Site Index  |  RSS
    TechTarget provides technology professionals with the information they need to perform their jobs - from developing strategy, to making cost-effective purchase decisions and managing their organizations' technology projects - with its network of technology-specific websites, events and online magazines.

    TechTarget Corporate Web Site  |  Media Kits  |  Site Map




    All Rights Reserved, Copyright 2000 - 2009, TechTarget | Read our Privacy Policy     		  TechTarget - The IT Media ROI Experts