A method for data storage includes receiving a plurality of data items for storage in a memory, including at least first data items that are associated with a first data source and second data items that are associated with a second data source, such that the first and second data items are interleaved with one another over time. The first data items are de-interleaved from the second data items, by identifying a respective data source with which each received data item is associated. The de-interleaved first data items and the de-interleaved second data items are stored in the memory.