4TB drives coming out....

Perhaps you deleted the log files at some point in the past?

At some point, to work around a persistent problem with non-automatable backups I wiped the system and started fresh. However, since that point I don't think I wiped the logs. They go back to 2011.

If the expansion you are seeing is at that reset date, then it probably is the initial size.

^ Unfortunately the occurrence of "Extending" was about 14 months after the first record in the log file. Bummer, it sure would be nice to be certain about the ultimate size limit (sans a wipe)...

Bump. There surely must be a way to determine the initial total volume size (so that maximum expandable size can be determined).

Regrettably I don't know of one. If someone does, it'd be great to post it.

Is there some educating guessing possible to determine my ultimate size limit? I hope to avoid a complete back up and restore and make the best financial plan for upgrading to 3TB or 4TB drives or some combination.

-Today I have 4 2TB drives. My system reports 81% of 5548 GB used.
-The only "Extending" line in my logs shows extending to 5.44TB
-I would guess this was adding a 4th 2TB drive to 3 existing 2TB drives?

Start with 3 x 2TB = ~4TB total storage
4 x 4TB = ~12TB total storage (~8TB greater than starting point)

It is totally fine to begin replacing 2TB drives one by one with 3TB drives, correct?

I will see more storage just replacing a single 2TB->3TB, correct? How much?
Even after largely filling a 4 x 3TB configuration, I could then proceed replacing with 4TB drives one by one?

Given the cost differential I think I'd like to proceed with the 3TB drives for now.

Thanks kindly!

Assuming single redundancy...

Inserting the first 3 TB drive you will see no increase.
Inserting the second 3 TB, you will see an increase up to about 6.37 TiB (~7 TB)
Replacing all 4 will bring you to about 8.18 TiB (~9 TB).

Often inserting larger drives is more cost effective.
For instance, at the moment a ST3000VN000 can be purchased in the US for about $130, and ST4000VN000 for about $170.

Adding 2 ST4000VN000 to your current array would cost $340. You need 3 ST3000VN000 to get the same volume increase - which would cost $390.

^ Thank you kindly!