Hi,

 

If I were to have the following three hard disks what would be my usable Hard disk space?

 

Disk 1: 1TB

Disk 2: 1TB

Disk 3: 160GB

 

Would I get 2TB as usable space or 160GB or something altogether different?

 

What should I do to get 2TB of usable Hard Disk Space?

 

Thanks,

Srikanth Koka

Hi,

 

If I were to have the following three hard disks what would be my usable Hard disk space?

 

Disk 1: 1TB

Disk 2: 1TB

Disk 3: 160GB

 

Would I get 2TB as usable space or 160GB or something altogether different?

 

What should I do to get 2TB of usable Hard Disk Space?

 

Thanks,

Srikanth Koka

Basically, the parity disk does not store any of your files, and is can not be considered as storage space for your data. Additionally, it must be as big, or bigger than any of the other drives in the array.

 

For that reason, your 160Gig drive cannot be used as the parity drive.. it is smaller than the other two drives in your array.

 

The only configuration you can use with those three drives, is to use one of the 1T drives for parity, and the the remaining 1T drive and the 160Gb drive for data.

 

You will get somewhere around 1.16 Gig of space.

 

To get 2T of storage for data, you need to add a third 1T drive in place of the 160G drive (or in addition to it if you purchase a "plus" or "pro" version of unRaid)

 

There is one other way to get 2T of data storage with those three drives, and that is to not assign a parity drive at all, and to use both 1T drives for data.  Of course, you are not protected from a disk failure in any way...  The real benefit of unRAID is the protection it offers from a disk failure.

 

Remember, there are only two kinds of hard-disks in the world...

 

No, not IDE and SATA...

 

The two types of hard disks are:

Those hard disks that have already failed... and those that have not yet failed... but will eventually, it is only a matter of time.

 

Joe L.

 

The two types of hard disks are:

Those hard disks that have already failed... and those that have not yet failed... but will eventually, it is only a matter of time.

 

Joe L.

 

I luv that quote about two types of hard disks. I have had my fair share of the first type of hard disks already, hence the need for unRaid.

 

Thanks for the reply. I now get it. I need to set the biggest disk as the parity disk and then I can add as many disks as I want as long as it is not larger the parity disk.

 

I am guessing that it should be possible to add a bigger disk later and move the parity disk to the new bigger disk. Am I correct?

 

Thanks,

Srikanth

Yes, at any time you can purchase a larger parity disk and put it in the parity slot and re-compute parity.

 

If (when) a "data" disk fails, you can replace it with a disk as large or larger than the failed disk, as long as it is not larger than the parity disk.  If the replacement disk is bigger than the parity disk, even by only one block, then unRAID supports what is called a "parity-swap" process.  You put the new larger drive in the parity slot, the old smaller parity drive in the slot that had the failed drive.  unRAID will then first copy parity from the old parity drive to the new, and then it will re-construct the contents of the data drive using the parity data in combination with the data on the other drives.  This takes even longer than initially computing parity, but it makes it possible to use larger drives are they are manufactured.  You don't have anything to worry about for a while, I've not read of anything larger than 1TB drives, at least so far.

 

Joe L.