Please help me out in storage issue in ovirt.

I am using Dell PowerEdge XD 720 servers, as node in Ovirt. Every node has 24TB storage space, so i am using all this space as the local storage in that.. But still i am facing the problem in storgae performance. My guests os are very slow to write the data.

So please give me, some tips using them i can increase the performance in storage.

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