Troubles while building RAID

Hello there,

I am new to OMV. I play a bit with it as a virtual machine and I really liked it. I want to deploy it on my server, but I have the following problem:
My server has 1x 250GB disk, on which is OMV installed and 4x 2TB disks, from which I want to build a RAID5. Everything seems to be fine. The disks are visible under "Physical Disks". I did a quick wipe on every one of the 2TB disks. And then I started to build the RAID. Under RAID management I click on "Add", all disks were visible, I checked all of them, named the RAID and clicked OK. I received a message that I have to wait until the sync completes. Everything seems to be fine so far.
Now comes the problem. I noticed that the sync speed is too slow (~15MB/s) and is falling (slowly but falling). As much the sync speed is falling the more slowly respondes the GUI when I call RAID management. On the other options the response from the GUI is instant, but from the RAID managenemt I have to wait about 10-20 secs. And from a certain point of time further the RAID management does not respond anymore. I receive an error "General Communication Error" (or something like this). And this is only when I call RAID management from the GUI. If I click on another option the GUI answers instantly. When I restart the server, I can open the RAID management again and see there that the sync is in status "PENDING". When I click to recover the RAID the sync goes further, but in a minute or two the RAID management stops responding again and return "General Communication Error".
I though there are some rests from the last partitions of the disks. I checked all of them and they are completely empty (no partitions, nothing). S.M.A.R.T. check shows them as healthy at 95%.
I really cannot understand the cause of this behavior. I tried to reproduce the issue in a virtual environment. I installed OMV on a Hyper-V VM and attached 4x 2TB virtual disks. The sync speed was about 200MB/s and the reponse time of the RAID management was instant.
Could you please give me some advise what can I do to solve this issue. I really like OMV.

Thanks in advance.

Hello.
Sorry for the delayed answer. I was out of the city for some days.

Here is the requested output:

Personalities : [raid10]
md0 : active raid10 sdd[3] sdc[2] sdb[1] sda[0]
      3906765824 blocks super 1.2 512K chunks 2 near-copies [4/4] [UUUU]
      [>....................]  resync =  0.0% (748800/3906765824) finish=8697.4min speed=7484K/sec

I started a new RAID10 to check, if the problem is in my server machine, because it is not that fast and it takes time to calculate the parity.
On RAID10 it is a bit a faster. It started about 10MB/s, the it droped to 1-2 MB/s, then raised again to 30-40 MB/s (which is pretty much in my case).
I set speed_limit_min to 50000, but this speed is never reached anyway.

I am not doing anything else on server. Just syncing the RAID.

The parity of a RAID5.
At the moment I started to sync a RAID10 and it is doing better. It syncing stable around 20MB/s.

It is a HP Proliant MicroServer.
AMD Turion DualCore 1.3GHz

A RAID10 sync is running since almost 2 hours and it has synced 2%. With this speed it will be synced about next weekend.

This is the otput of dd:

root@vault:~# dd if=/dev/zero bs=1024 count=1000000 of=file_1GB
1000000+0 records in
1000000+0 records out
1024000000 bytes (1.0 GB) copied, 7.347 s, 139 MB/s

Zitat von subzero79

http://www.cyberciti.biz/tips/…resync-rebuild-speed.html

Take a look here, usually mdadm sets speed not to slow down the rest of the system. This can be override.

I followed exactly the same guide, but it did not improve anything.

I set /proc/sys/dev/raid/speed_limit_min to 50k, but they are never reached. The top speed I reached was about 30k.
The server is completely idle. It is a fresh installation and nothing is running on it yet.

I found what is issue was. One of my hard drive was bad and caused the troubles. Strange was, that I ran several S.M.A.R.T. checks and they showed it as healthy. I removed it and now everything is working as designed.

Thanks for the effrots guys.