SOLVED Free hard drive dock space

[bobbob]

I'm trying to plan my first build, and I'm trying to figure out the number/type of my storage devices. I've read in several build threads where someone comments that its good to have at least one free hard drive bay. I've read the freeNAS User Guide with respect to replacing drives, and have the following question: Is the only benefit (as far as freeNAS is concerned) in having a free bay is if you are upgrading an existing (and online) drive to a larger one?

 

[Kevin Horton]

A free slot would also be useful if a drive was starting to show signs of impending failure, but had not failed yet. If you remove the failing drive, you lose one drive of redundancy until the resilver process is complete. If you have a free drive slot, you could put the new drive in, and have FreeNAS use it to replace the bad drive, without losing redundancy during this transition.

 

[bobbob]

Thanks - makes sense. I realized from reading your answer I need to read about drive monitoring and testing, but if you wouldn't mind a follow up. Do drives typically show signs of failure before they fail, and do drives that are showing signs of failure typically fail? Or is it more of a grey area: drives showing degradation may or may not fail, and whether or not to replace the drive is dependent on how important your data is.

 

[Kevin Horton]

I have no personal experience, but I have seen many users on these forums reporting drives that develop an increasing number of unreadable sectors as time passes, as seen in the results of SMART tests. This is normally considered a sign of a drive that is near the end of its life, and may fail completely at any time. I've also seen other users that had drives fail with no warning.

Once you have your system running, you should set up FreeNAS to do automatic, periodic SMART tests.

 

[bobbob]

Thank you so much for your replies and info. I have a lot better understanding, and can make a more informed decision (likely will plan to keep a slot free).