VA7410 sudden reduction of I/O throughput

[tkc · Accepted solution]

your RAID 5 DP Allocation has dropped tremendously during that time. you have used up the free space in the array that made the array to start busy modifying existing data from RAID 1/0 to RAID 5DP. do you have some spare disks for this array? try to add more disk space to help the writing process perform better.

[tkc]

your 'RAID 5 DP Writes in Place' was also high during that time. Write in place means you are writing onto existing RAID 1/0 space as RAID 5DP. So these writes are basically read, modify before actual write which is why the whole process of writing is that slow. This will help preserving the much space needed now in the array because of more writes. i can't suggest much other than adding more disk space or you can write to the array for abt 20 mins, let it stop for a while for the array to optimise its space and do the writing again at a later time.

[karza167]

Thank you for the explanation! Now that I have some understanding how the Autoraid works, your reasoning makes perfect sense.

In this case we don't have a possibility to add any HW to the array. Also because of the intended usage of this array, it is not an option to write to the array the way you suggested. On the other hand, it is possible to reformat the array and choose the RAID 1+0 option which should have a more consistent throughput.

I was able to download the documentation and also found some posts in this forum how this can be done. While at it, I'll probably have the firmware upgraded as well.