topic Re: Data Size In Raid 5 in Disk Enclosures

Data Size In Raid 5

susee_sundar — Wed, 12 Jul 2006 04:53:53 GMT

Hi.,

As per my Knowladge Minimum 3 disks are required for Raid 5 configuration...
Such that we will get 2 disk_size of data & 1 disk_size is lost for striped parity..

HERE I am having 3 disks of size 80gb , 40 gb & 40 gb...

Here How much data size we will get for the FS...

Surya...........

Re: Data Size In Raid 5

Arunvijai_4 — Wed, 12 Jul 2006 05:00:28 GMT

Hi Susee,

Check this document for more information : http://www.pcguide.com/ref/hdd/perf/raid/levels/singleLevel5-c.html

-Arun

Re: Data Size In Raid 5

Uwe Zessin — Wed, 12 Jul 2006 05:08:38 GMT

You will get 80gb - the total size is defined by the smallest disk drive in a traditional RAID set.

Re: Data Size In Raid 5

Lethuillier — Wed, 12 Jul 2006 08:39:42 GMT

As Uwe quoted, the total size is defined by the smallest disk drive in a traditional RAID set. So your datasize will be 40Gb x 2.

But ...

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 40 Gb disks really hold about 37 Gb.

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 three disk set has the space of two disks, or 2x37 Gb.

But ...
Remember, too, that filesystems and volume managers have some overhead. Expect to use about 72 Gb on your RAID set.

Re: Data Size In Raid 5

susee_sundar — Thu, 13 Jul 2006 00:26:10 GMT

Thanks For All...