So I can't afford to replace the drive at the moment and I think my parity drive is dying.

 

1. Can I start the array without the drive temporarily? Like its an emergency and I need a file off of it.

 

2. If not how would I put a drive into my computer and read the data off of it. Is it a special format that I'll need software to read in Windows? I assume so.

1. Can I start the array without the drive temporarily? Like its an emergency and I need a file off of it.

 

Yes - the array will run missing any one disk... although performance may be degraded.  Also - please please remember that any other disk disasters, and you're looking at real data loss.

1. Can I start the array without the drive temporarily? Like its an emergency and I need a file off of it.

 

Yes - the array will run missing any one disk... although performance may be degraded.  Also - please please remember that any other disk disasters, and you're looking at real data loss.

 

Understood.

 

The thing is shut down for now but I think I have a couple of important files on it I need to grab real quick then back down it goes until I can afford the replacement drive.

 

I knew it could boot missing a data disk just wasn't sure about the parity disk.

If all else fails I guess I can fall back to manually getting data off the disk. I assume thats still possible I remember it being listed as a benefit of the unraid setup.

The parity drive contains no "real" data, but has information on the sum of all the individual bits on the other drive.  So let's say you have 8 drives + parity, and for the same individual bit location, each of the disks are as follows:

Bit 1: 1 + 1 + 0 + 1 + 0 + 0 + 1 + 1 = 5 = odd (stored as say 1)

Bit 2: 0 + 1 + 1 + 1 + 1 + 0 + 0 + 0 = 4 = even (stored as say 0)

and so on...

 

The odd/ even data is stored on the parity drive.  If drive 1 were to fail, the system would know:

Bit 1: x(unknown state) + 1 + 0 + 1 + 0 + 0 + 1 + 1 = x + 4 = odd, therefore x = 1

Bit 2: y(unknown state) + 1 + 1 + 1 + 1 + 0 + 0 + 0 = y + 4 = even, therefore y = 0

and so on...

 

Thus UnRaid is (slowly) able to calculate the state of the missing disk, and rebuild it.  The array is even able to run without the drive by calculating the state of the missing disk 'on-the-fly'... but as you can imagine, this calculation has to be done in real time for each bit of data accessed, thus massively degrading the array performance.  Note if parity is lost, then no actual data is lost, and the parity will just need to be calculated on the parity disk when replaced.

 

The system (currently) works on the basis that a byte can only have one of two states, 1 or 0, and therefore is the state needed to get to the odd/ even state in total.  However if you lose 2 (or more), the the solution to the "equation" is no longer unique, so the drives cannot be rebuilt.

 

If all else fails I guess I can fall back to manually getting data off the disk. I assume thats still possible I remember it being listed as a benefit of the unraid setup.

 

Yes - all data on 'good' drives are available by connecting them to a PC (SATA in a desktop/ USB adaptor for a laptop) - this isn't possible with normal RAID, and is one of the benefits of the UnRaid system.  So as it currently stands for you with a dead (or dying) parity drive, you've had no real data loss.  But if you lose another drive you end up with ? + 1 + 0 + ... = ?, which is a very unhappy place to be!

Obviously I'd be very unhappy if another drive failed.

 

One last question and I have all the info I need to get my couple of files and leave the server alone until payday when I can replace the bad drive.

 

I did NOT label which drive is which so I removed what I THINK is the parity drive.

 

Anyway to tell?

 

I put it in my drive dock in Windows and opened it in the ReiserFS browser...t he YAReG thing and it shows nothing on the drive at all just says

 

drive3part0

 

Does that mean its the parity drive?

Screenshot attached

 

Likely, although I'll defer to someone more expert on this!

 

I should think the most foolproof way to check is to fire up the array and look in the listing - the failed drive should be clearly indicated.  I understand why you wouldn't want to take the unnecessary risk in doing this though...

Okay got my head screwed on straight now. It was the parity drive as it was the first drive plugged into the board.

 

Hopefully this weekend I bring the server back online.

 

If I replace the parity drive with this

http://www.microcenter.com/single_product_results.phtml?product_id=0349903

 

Is there anything special I have to do to it? Jumper wise. I know there were changes with drives recently.

There are potential problems with the F4 drives. You may want to avoid them for a while. Check the good deals forum for places to get Hitachi 5300 for around the same price. That's what I did recently.

 

Or take a spin around the HD forum and read about the F4s.

 

If you are happy to get a DOS boot USB drive working to update the F4 FW then you should be okay with the F4. You may want to disable write caching on it just to be sure.

Sucky. Cause thats what on sale locally.

 

Hrm....

 

 

thanks for the info btw

 

 

edit:

 

Ordered this instead.

 

http://www.microcenter.com/single_product_results.phtml?product_id=0350052

annnnnd they were out of the drive it seems.

 

Looks like I may have to go with an EARS drive.

Its just a jumper thats required for them right?

If you are running 4.7 then set the partition alignment to 4k-aligned (it's on the option page closer to the bottom). You don't have to change this back and you don't have to use jumpers on the EARS drives.

 

Otherwise, install the jumper.

 

Peter

If you are running 4.7 then set the partition alignment to 4k-aligned (it's on the option page closer to the bottom). You don't have to change this back and you don't have to use jumpers on the EARS drives.

 

Otherwise, install the jumper.

 

Peter

 

Cool beans. So I'll bring it back up with the parity drive and upgrade to the 4.7 then do that.

 

That a safe path?