Jump to content
Shehryar

UnRaid vs Raid

5 posts in this topic Last Reply

Recommended Posts

Newbie here...

  • I want to know what is unraid and how it differs from raid.
  • Which is better raid or unraid
  • i understand how 1 parity drive can be used to recover data if one drive fails but if two drive fails will the data on those 2 drives are lost can we recover it using parity drive
  • how 2 parity drive works and how 2 drives can be recovered when 2 drives fail
  • and can you link some articles and videos and anything related to unraid that will help me understand more about unraid like i said i am a newbie

 

Share this post


Link to post
1 hour ago, Shehryar said:
  • I want to know what is unraid and how it differs from raid.
  • Which is better raid or unraid

Basically, Unraid uses a even-parity calculation across all the data drives to be able to reconstruct the failure of a single data drive.  See here for how it works:

 

        https://wiki.unraid.net/index.php/UnRAID_Manual_6#Parity-Protected_Array

 

Raid is faster in data writing and retrieval operations.  However if two drives fail in a RAID configuration, you lose all of the data in the array.  Also all drives must be the same size. 

 

With Unraid, writing is much slower and the read process is limited to the read speed of the data drive which contains the actual file data.  Also if two drives fail, you only lose the actual data stored on the drives which fail.  The data on the other drives can be read on any Linux system.  The capacity of the data drives can be different as long as the parity is as large or larger than the largest capacity data drive.  It is also quite easy to add capacity to any Unraid server by simply adding another data drive.  

 

1 hour ago, Shehryar said:

i understand how 1 parity drive can be used to recover data if one drive fails but if two drive fails will the data on those 2 drives are lost can we recover it using parity drive

In some cases, it is possible to recover some of the data from the failed drives depending on the nature of the failure.  But it is best not to count on it. 

 

1 hour ago, Shehryar said:

how 2 parity drive works and how 2 drives can be recovered when 2 drives fail

The second parity drive uses a Reed-Solomon encoding scheme (which is basically a very complex matrix operation) to allow reconstruction (in use with the first parity drive) to be able to rebuilt two failed drives at the same time.  If you wish to know more about Reed-Solomon, you can google it!  (You will need the equivalent of a college degree in Mathematics...) 

 

One import thing to realize is that parity protection is NOT a substitute for a reliable multiple-copy backup scheme with one of those copies being in a remote location.   Just think of having your server in a house fire, flood, hurricane or being stolen.  It is also not a replacement for a due-diligent administrator who monitors his servers and sets up all of the notification services so that he receives the earliest possible notice when any problem arises!  

  • Upvote 1

Share this post


Link to post

so we can recover data on the 2 drives if 2 drives fails if we have 2 parity drives in Unraid

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now