Please let me preface by saying that I understand poorly formed reports can cause poor SSRS performance and I have people looking at that issue separately.
I have an SSRS server that is seeing incredible high IOPS at certain points in the day. The ability to quickly run reports pretty much stops until the IOPS return to normal. The MSSQL database is on a separate AWS instance (two systems running, SSRS and MSSQL). The SSRS server has more than enough RAM and CPU, those never spike. It is only the C:\ (where MSSQL SSRS is installed) that is seeing the issue. When I say that there are IOPS spikes, I am seeing IOPS writes from from ~20k to ~32k. Those spikes occur while the queue length also increases.
Can someone suggest configuration changes to make SSRS use a secondary drive for whatever it is doing to cause the high IO? Another possibly important piece of information, in the logs I often see the message "Call to CleanBatch()"; it often lines up with the IOPS write spikes.