As users will know, unRAID takes a lot of time to sync parity or do anything else of a similar nature, such as restoring a failed drive or replacing a drive with a larger one. Is it safe to access unRAID during this process? I assume that reading is fine (other than on a data disk that's being re-created), but what about writing?

 

I think I read somewhere that this can be done, but I can't find the reference now. So far, I've avoided doing anything on unRAID during such processes, but that's largely out of superstition. I'd like to find out what the official line is.

Yes, you can safely use the array while restoring/replacing.

 

It has been a while since I added a new drive, but I think the when a new drive is being cleared the array is not on-line and you cannot read or write to the network shares.

 

Other than that, you can read or write to the array while it has a "broken/missing" drive, or when it is calculating parity, or while it is rebuilding a drive that has failed.  Reading will be slightly slower than if the array has all its drives online, but it will work just fine.

 

You can even "write" to the missing drive when a drive fails.  As far as windows is concerned, you can read or write normally.  When you eventually put a new drive to replace the missing/broken drive, the data, including any newly written, will be restored to the replacement drive.

 

I did an experiment in that I served 4 different movies (DVD ISO images) to 4 different media players on my LAN from a drive I removed (unassigned actually) from my unRaid array.  The unassignment simulated a failed drive.  It worked just fine. The DVDs played as if the drive was present.

 

I then re-assigned the drive and again served 4 different movies from the missing drive while it was being rebuilt.  As I said, it kept up just fine.  Since the odds of more than two movies being played are slim (only two of us in the house) we will never even know of a failed drive unless we go looking for it.  That is exactly why I set up my server to send me an e-mail if a drive fails.

 

Joe L.

Thanks, Joe. Kids permitting, I'll be upgrading one of the drives to a larger one soon.

 

Are you saying that as soon as I can "see" the upgraded drive from Windows I should be able to write to it? Wouldn't it take some time to format the drive, or is this done on-the-fly?

If you are upgrading an existing drive the new drive is not formatted.  It is probably cleared first, then the old drive's contents written to it as calculated from the parity drive and the remaining data drives.  The contents written include all the data blocks, including those that define the partitioning and the formatting.

 

Because of that, there is no need to pre-format a replacement drive, as the formatting would just get overwritten by the old drive's.

As soon as you see the drive in windows you can use it.

 

There is one thing to consider though.  Drive failures frequently occur in the first few days of their lives.  With that in mind, I would not put your most critical non-replaceable file on the new drive until parity re-build is complete.    If you were just ripping another DVD from your collection, go for it.

 

Joe L.

 

Thanks again, Joe.