Adding to Ivan's comments, it's unfortunate, but many ShareCenter owners who visit these forums perform firmware upgrades for no other reason than wanting the latest and greatest version. Because of this unfortunate fact, when upgrade questions come into play, we always ask the question "Why are you upgrading?" No disrespect was intended. We're only looking to educate members and provide advice that will best protect their data.
I purchased my first DNS-343 in 2008 and was running firmware v1.02. I just read through some of my first posts in this forum back in 2008 to validate that! I incrementally upgraded the firmware to v1.05 over the years and never had to reformat the HDDs. I still have two legacy HDDs (1.5 TB) in my first DNS-343 that were not formatted since 2008. That said, all 8 HDDs in my two DNS-343s are configured as Standard Volumes.
It's possible (I can't confirm) that upgrading legacy firmware may not be as forgiving to more complex configurations (i.e. RAID, JBOD). I haven't personally tested firmware migration jumps spanning multiple versions nor have I tested migrating firmware with more complex HDD configurations. When it comes to the ShareCenter line in general, HDDs configured in Standard Configuration are usually easier to work with than the more complex alternatives.