Free space today cannot tell you when the drive fills up. Save daily file sizes and let a short query turn the growth into a date.
Finding Oversized Data Files With Lots of Free Space
Identify oversized data files with FILEPROPERTY, separate internal free space from disk capacity, and review one-time shrink choices.
Log File Growth and Instant File Initialization: The 64 MB Rule
The 64 MB rule says log file growth can skip zeroing when instant file initialization is on, but only up to 64 MB. Two trace flags make the SQL Server error log show a 64 MB growth skipping the zeroing and a 65 MB growth zeroing in full. The last section says what to change.
Database File Latency: Read and Write Stalls per IO
Database file latency is the stall time per read or write. This post divides the IO stall columns by the call counts for every file, explains the zero queued columns and says when a number is worth acting on.
Will the Next Autogrowth Fit? Checking Growth Against Free Disk
The drive has free space, yet the file will not grow. Here is how to calculate the next autogrowth and test it against disk and MAXSIZE.
Read-Ahead Reads in STATISTICS IO: What They Tell You
Interpret read-ahead reads in STATISTICS IO, compare isolated cold scans and seeks, and separate prefetch from storage-wait evidence.
CHECKPOINT Covers One Database: Flush Data to Disk
CHECKPOINT covers one database, so to flush data to disk you run it in each database. A demo with two databases shows one flushed and one still dirty. A short script then flushes every database in one pass, and the post says when a flush is worth it.