corruption in indexes under heavy load

We're writing a large amount of data to a number of tables in PG 9.3 on Windows Server 2012 R2 and then, immediately after, creating a number of indexes (there are no indexes during the initial data write). The data we're writing exists in files on the same drive as PG's data.
During the index creation we're seeing write latency on the storage up to 1500ms (during the data write it may go up to 200ms, possibly due to reading the data from the same storage). The write latency is being investigated separately as there's no way it should ever get that high.

There is no indication in the PG log that anything is amiss while creating the indexes and there are no clients accessing or updating the data at this time, although there are a number of instances of "pgstat wait timeout" around the time of the high write latency. Therefore we must assume that the indexes were created successfully.

We're fairly convinced the issue lies with the actual storage but I was wondering if there is anything within PG that would be affected by the high latency and result in corrupt indexes.

Regards,
Russell

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