The HR21 series require a 3Mbps transfer rate, and a number of drives come out of the box set with jumpers at 1.5Mbps (common to PCs).
If you have a drive that can be changed to (jumper) or is configured at 3Mbps...then you should be fine using it with the HR21 series - eSata. As for using one internally....the tech requirement is the same, but then there's that voided warranty thing....
AFAIK, every 1TB SATA drive is fast enough.
Do we know of any of them that come with default settings that force them to run slower? (I don't, but maybe I missed something.)
AFAIK, the default settings out-of-the-box for modern high-capacity bare SATA drives are the fast setting.
You state that "a number" of them have slow defaults. Is this really true? If so, which ones?
We see cases of people getting confused because they think they need to mess around with jumpers when they shouldn't be doing that.
AFAIK, for modern high-capacity SATA drives, people should not be messing with jumper settings, but maybe I missed something somewhere.
If you know of any cases where people have to mess with jumpers, please post what they are.
No. Don't assume that. But whatever configuration works, it works for all HD DVR models.
Am I correct in assuming that just about any eSATA setup will work with the HR20-700?
This is a false statement.
There are multiple reports that permit us to conclude that various configurations that work with HR20's do *not* work with HR21/HR22's.
The truth appears to be that most-but-not-all eSATA's work with HR20's, but many of those do not work with HR21's.
This very problem of inconsistency between HR20's and HR21's is exactly why this FAQ got started.
The fact is that HR21's (and evidently HR22's) have been a lot more picky about what eSATA drives they work with.
Please don't tell people otherwise, because that's simply not true.