Might seem like a dumb question to you more savvy puter users.

 

Just wondered as I'm close to filling up my first drive (500Gb). 

 

While I'm here, I'd also like to ask about the parity info - does it take up space?  What exactly is it?

1.  How much space should I leave on a HDD?

 

Well, if you surveyed this forum, I suspect the answer you would get is "NONE". ;-)

 

The real answer (at least from me) is, "as much as you need".  If you generally use your drives primarily for "reading" data (aka movie playback), then there's no real reason not to fill up the disk.  If, on the other hand, you use your drives for "reading & writing" data (aka frequently updating files), then you should leave some slack space on the disk to allow you to safely save updated files.

 

2.  While I'm here, I'd also like to ask about the parity info - does it take up space?  What exactly is it?

 

I'll let someone else handle boolean math 101, but suffice it to say that parity information is calculated from individual bits (zeros or ones) on your drives (so yes, it does take up space).  This resulting value allows unRAID to protect you in case of a drive failure, by "filling in" the missing information.

Bill, I think he may have been wondering how much space that parity info takes up on the data drives (if not, I apologize).  Parity is stored exclusively on the Parity drive you assigned, not on the data drives, so you never have to reserve space for it.

 

Hey...thx so much for the answers.

 

I wasn't sure how much space I needed to leave, if any.  My unRAID is a video server used only for reads (after the massive backup sessions I've been having  ), so being able to fill it right up is great.

 

I figured the parity stuff would be zero/ones of some description.  I have wondered why the parity drive always shows the "free" field as "-" and not the space it takes. 

 

Thx again

 

 

I have wondered why the parity drive always shows the "free" field as "-" and not the space it takes.

The parity drive protects every sector of every data disc. The parity drive doesn't care (or even know) which sectors on the data drives are filled with valid data/files and which are not. Because of that the parity drive never has any free space left.

Bill, I think he may have been wondering how much space that parity info takes up on the data drives (if not, I apologize).

 

looks like you're right RobJ.

 

flambot,

 

As RobJ indicated, all parity information is stored on the parity drive, so you don't need to worry about setting aside space for it.  But as madshi said, it protects every sector of every data disk.  This, in turn, explains why the parity drive has to be equal to or larger than any single data drive.