It depends on the POH (power-on hours) more than the actual age

It’s a vhd, you can mount it and browse for files

If you just want a compressed system image, Windows has this functionality built in. Control Panel > Backup & Restore (Windows 7). It’s basic but free. It doesn’t support versions or multiple images so you have to change folder names if you want to keep more than one image.

Your explantion of the problem is ambiguous.

On each disk there is a hidden PoolPart folder. In Windows explorer you must enable view > hidden folders to see it.

Everything in these folders is part of your Pool. Anything on the disks but outside these folders is ‘Other’.

If you want to force files into the Pool - for example using another system which does not have Drivepool installed - you have to move them into the hidden poolpart folder. This practice is discouraged because it can confuse Drivepool or cause errors. But if you must do it follow the instructions on Drivepool website/forum.

For light workloads SSDs are more reliable and long-living than HDDs. They have no moving parts.

Prior to 2011 the trend was for GB/dollar to double very 14 months. (source mkomo.com/cost-per-gigabyte)

Post 2011 the trend is for GB/dollar to double every… 10 years maybe.

The HDD market went to shit due to mergers and price-fixing.