I have sequenced a few samples using hiseq4000 at Novogene. Standard output size is expected to be at least 150G/lane. I got only ~70G. Novogene's explanation was that something might be wrong with the reagents. Instead of repeating the whole run, Novogene only agreed to run another 60G using lane sharing on Novaseq 6000. They said you can used the previous run plus these new reads to do data analysis. Illumina is strongly against this "smart idea". I don't even know how to combine the two FASTQ files. Seems like their interests are only to save costs but not customers' benefits. I had to pay half of the lane price to ask for another hiseq run, which is obviously unfair but I need the data asap. Unfortunately, the second run did not make any improvement. They explained that the lane might have been underloaded because they used the old concentration values in the repeat. It is totally waste of time and money. They usually offer lower prices than other vendors but if one has encountered this type of problem, the price won't be low any more. Besides, do you trust the data?