I'm sure the answer is yet but I can't find my answer. Is it okay to write data to the drives during a Parity-Sync? I just got my unRAID server running with 2 drives, one being parity, and it shows it has about 17 hours to do the Parity-Sync. Am I okay to write to the data drive during this? I have a done of files I need to move off my media center so I can free up space for recordings and I basically have none since it's full.

Actually I guess I got my answer. It doesn't allow you to.

Actually I guess I got my answer. It doesn't allow you to.

Yes, you can write to the array during a parity sync.

 

The only time you cannot is when the array is stopped, or when it is clearing a new drive for you (you did not pre-clear the new drive, and it does the clearing step for you)

 

Other than that, the array is available for writing and reading.  (as long as you set the share permissions to read/write)

 

Attach a syslog to your next post if you are still unable to write to the array.

Seems to be working okay now. I left it do the sync through the night and now writing it is working. Before I was getting an error in Windows about not being able to write and it would only create folders, but no data. When it would copy data, I was getting less then 1 MB in speeds.

 

Now that it is writing, I am seeing speeds only being 25 MB where when I was testing without a parity drive, I was getting about 60 MB. Is that pretty number of a decrease with a parity drive compared to not having a parity drive?

I am seeing speeds only being 25 MB where when I was testing without a parity drive, I was getting about 60 MB. Is that pretty number of a decrease with a parity drive compared to not having a parity drive?

Quite normal rates.

Cool. Just wanted to make sure.

Is it a good idea to?  It's always seemed risky to me... having all the drives chugging along at full speed, and all of the sudden two of them have to divert in half... 

Is it a good idea to?  It's always seemed risky to me... having all the drives chugging along at full speed, and all of the sudden two of them have to divert in half... 

it will slow down the parity check a time bit, but it is very normal for disks to handle more than one task at a time.  In my own experience playing a movie will slow down the parity check speed by a few MB/s but other than that, no impact.

 

What do you think will happen if you ever attempt to watch more than one movie at the same time from the same disk?

 

Joe L.

Look at windows for example.

 

You are watching a video, get an email and in the background your machine is cache'ing files all over the place to offload other things. Heck in the old days when we didn't have a lot of RAM your machine would be swaping like crazy.

 

I notice now and then a slow down in either transfer speed or pairty, but nothing I can't live with.

Think about it like this.  My media centre will be recording up to 4 programs and potentially playing back 2. One on the media centre, 1 on a media centre extender.  All that should happen is things slow down when you are writing parity. The parity check will take longer and your writing to the data disks will be slower as well. The only time this is likely to be a problem is if the data you are writing to the disk is time critical like a tv program being streamed off air. If you cant write fast enough you will lose some. That said, you shouldn't have any problem just copying files to the unRAID.

I suppose enough's already been said, but there's a simple way to see the effects of doing things that cause the disk heads to thrash (which is what happens when you write data or stream a movie during a parity sync, parity check, or disk rebuild operation).

 

On a Windows machine, copy a moderately large file (1GB or so) from one folder to another ON THE SAME DISK  (or if the disk is partitioned, do it from one "disk" to another "disk" that are actually on the same physical disk) ... and time the copy.    Now copy the same file from the same folder to a folder on a DIFFERENT physical disk.    You'll notice a HUGE difference in the time.  But both operations will work okay ... the first simply takes a lot longer because the disk head is thrashing with just about every multi-tasking time-slice.

 

Whether you NOTICE the impact is another story.  For example, if you stream 3 or 4 movies from the same disk, as long as each stream is "fast enough" (and it will be) there's no noticeable impact.  Same thing is true when writing to the system during a parity sync/check ... the write operation will be slower, but will still work fine, so you probably won't notice a lot of impact.    The ongoing sync/check/rebuild operation will take longer ... but that's not likely something that will be annoying.