During a sequencing run, the software writes a large amount of raw current data to disk in real time, hence the 1 TB SSD requirement when using a MinION Mk1D or Mk1B.

The files are further packaged into their final compressed file types, primarily POD5, FASTQ, and BAM files. The sequencing script progresses until all files have finished processing, the run is stopped, or basecalling is stopped. You can find more information in the Data analysis technical document.

The final disk usage will depend on the average read lengths and shorter fragment reads take up more space per Gb. These are approximate figures with default MinKNOW options and .gzip compression of FASTQ files, assuming ~20kb N50:

• POD5: Every 1 Gbase of sequence data takes up ~4-7 GBytes of space.
• FASTQ: Every 1 Gbase of sequence data takes up ~0.65 GBytes of space.
• aligned BAM: Every 1 Gbase of sequence data takes up ~1.4 GBytes of space