For Cannas, the rhizome is used by gardeners to propagate the plants by a process known as vegetative reproduction.
So how does a rhizome differ from a bulb? A bulb is an underground vertical shoot that has modified leaves (or thickened leaf bases) that are used as food storage organs by a dormant plant. A Canna is never dormant, it is growing 52 weeks of the year. That is the bit that so many get wrong when handling their Cannas over the winter.
In the northern hemisphere, in England, our Cannas are growing outdoors for 6 months and spend the remaining 6 months being abused indoors! We see books and articles telling us to dry them out, cut of the roots and then leave them in boxes of peat until the spring. Watering is hardly ever mentioned. So all the Canna will be doing is draining its energy reserves stored in the rhizome to keep life growing. If it had a bad growing summer before it may not have enough food reserves to keep going and will just give up life. We have all seen rhizomes that do that.
There is an urban myth that says that if the first leaf in the spring is bad, then the Canna has virus. A little thought and understanding would reverse that, and the wisdom should be that a good first leaf indicates great health, but while early leaves may not be good, by the time the plant is growing with roots in well-treated soil if it is not producing better and better leaves, then it possibly has virus.
So whatever method you use to store your Cannas over-winter, I would recommend that you ensure that it is kept ticking over for that long winter period.