I have been dealing with computers since before the first IBM PC was introduced and one thing I cannot stress enough is, ALWAYS KEEP A BACKUP! Someday that hard drive is going to quit working and today we have access to the Cloud via Google Drive, DropBox and others. But when it comes to Sourdough we have to rely on simpler methods to make a back up.
Let's face it, things happen. Right?
What are some of those things? Bugs, heat, feeding and so much more can affect our starters which is why I always keep a small jar of starter in the fridge. It does not take much to reactivate a starter that's been stored in the fridge and my experience tells me a starter will last almost forever in the fridge.
Here is how you do it. When you feed your starter and you normally dump it down the drain instead pour it into a small clean canning jar and tightly close it up. Use a canning jar with appropriate lid. Fluid will separate but don't worry about the fluid.
To activate a starter from the fridge, scoop out a heaping tablespoon of cold starter and place it in a quart canning jar. Add 1 cup flour and (room temp) 3/4 cup spring water. Stir it up. Let it sit overnight and dump out half. Feed it another cup of flour and 3/4 cup water. Let it sit again. It does not hurt to feed it every twelve hours when reactivating your starter. Most starters will be very active in less than 36 hours.
Are you old enough to remember yeast cakes? A small package of yeast stored in a foil wrapping? When starter has been stored in the fridge for a while it has that consistency. Shows my age I guess.
All my starters (except two) use normal unbleached white flour. I do not use bread flour because I find my breads do better without the added wheat gluten. The exception to this rule is Chef Don's Megaheart Starter. He created his starter from grapes grown in the California foothills of Auburn, California and he used bread flour. I have tried to wean his starter off of bread flour to no avail. The other starter does is based on an Organic Dark Rye flour (Tara's).
So remember! Keep a back up in the fridge, no matter what. I use these flat canning jars because I can stack them three to four high on the shelf in the fridge.
How To Order My Sourdough Starters