Windows server 2016 raid 5 - supermicro cse-826be1c-r741jbod It takes really long to Resync

Question

We have connected supermicro cse-826be1c-r741jbod (twelve disks via two SAS lines) to our windows server 2016.
We created software raid 5 (total available disk space is 120TB).
I let it resync on weekends (two days) but on the Monday there is only 19% is complete!

Is there a way to see if everything alright? Is it normal that raid 5 resync takes soo long?
What can you suggest? Maybe there are some logs or something like that?

Answer 1

Hi,

Thanks for posting on our forum!

Based on your description, I think there is no problem with your disk or computer. There are many reasons that can lead to this slowness:

1) Due to the different performance of hard disks from different manufacturer, basically there is no guideline to show how long it will take to complete "Resyncing".

2) Software RAID-5 is notoriously slow and any other load on the system - CPU or IO - will slow it down even more. And I guess that the system is doing this as a very low-priority process in order to not overwhelm the rest of the system. If your system is Linux, from my research, this "Resyncing" process can be faster.

In addition, after my research, I figured it out that in reality, how much time one needed to finish its "Resyncing" varies a lot if you choose to use software RAID 5. I have seen someone who used 96 hours to complete his resyncing for 4 x 2TB disk array. In this place, your resyncing for 120 TB is relatively fast.

Here are the cases which are similar with yours:

https://serverfault.com/questions/291154/2008-r2-software-raid-5-writing-during-resynching

https://serverfault.com/questions/390294/mdadm-raid5-too-slow-when-writing

(Please note: Information posted in the given link is hosted by a third party. Microsoft does not guarantee the accuracy and effectiveness of information.)

My advice is, just spare 4 days to see if there can be any progress, if you observe that although the process runs in a slow pace, the process is continuously running. If so, your Resyncing is fine. Besides, maybe you can try to shut down as many applications as you can to reduce the load of I/O.

Finally, if you are too worried that you really want to check some logs, you can go to %SystemRoot%\System32\winevt to find out related logs and see if there are any error codes or messages.

Thanks for your understanding and support! And I would really appreciate it if you could help me Accept Answer to support my work! Have a nice day! : )

BR,
Joan

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