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Re: RAID 5 with different size disks



On Fri, 2006-02-03 at 08:23 -0800, Joel Jaeggli wrote:
> On Fri, 3 Feb 2006, Fajar Priyanto wrote:
> 
> > Hi all,
> > Is it possible to setup a RAID 5 array using different size disks? Such as hda
> > 9GB, hdb 36GB, hdc 40GB, hdd 80GB, hde 80GB.
> 
> if you think about it raid-5 is just a special case of raid-0 your 
> capacity is going to be limited by the size of the smallest drive... in 
> this case you'll get a lot more capacity just but setting up a mirror on 
> the two 80GB drives.
> 

Raid 5 and raid 0 are very different animals.

Raid 0 is striped.  Any single physical device fails and everything is
gone. There is no redundancy and multiple failure points.

Raid 5, while it is striped, also has a redundant parity stripe.  Any
single drive failing does not lose data since the lost stripe can be
rebuilt from the parity stripe. The data on any one drive is copied to
the parity stripe on all the other drives.  A single drive failure can
be tolerated with no data loss. In order for data to be lost this would
require 2 simultaneous failures. 

Very different in functionality and in redundancy/fault tolerance.

> joelja
> 
> > What are the impact and consequences?
> > Thank you very much,
> >
> 
> -- 
> --------------------------------------------------------------------------
> Joel Jaeggli  	       Unix Consulting 	       joelja darkwing uoregon edu
> GPG Key Fingerprint:     5C6E 0104 BAF0 40B0 5BD3 C38B F000 35AB B67F 56B2
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