Recording times HR20 vs. HR21

[msantarc]

I have two DVRs one is an HR20 ant the other is an HR21. I've noticed that they don't seem to have the same recording capacity, but everything I've seen on this form says that they should be about the same. I record everything in HD on both machines.
On my HR20, I currently have 12 hours of recorded shows and it shows 51% available space
On my HR21, I have 18 hours recorded and it shows 75% available space.
Rough calculations seem to show that the HR20 has a 24-25 hour capacity while the HR21 has abut a 72 hour capacity.
Is there something wrong with my HR20 or does this have something to do with the HR21's ability to receive & Play MPG4 (I dont know if the HR20 can do the same).
How can I find out what the hard Drive capacity is on both machines?

[russdog]

The amount of HDD space used per hour of recording depends on what's being recorded: SD vs. MPEG2-HD vs. MPEG4-HD.
So, just counting hours is not useful.

The HR20 and HR21 can each record all 3 kinds.

The HR20 might have a 300GB HDD or it might have a 320GB HDD.
The HR21 has a 320GB HDD.
So, depending on what's in your HR20, the 2 units will either have the same capacity, or the HR21 might have just a tad more.
There is a chart about hours in item #3 of the first post in this thread: http://www.dbstalk.com/showthread.php?t=142735

12 hours of MPEG2-HD would use more space than 18 hours of MPEG4-HD.
MPEG2-HD uses about 6GB/hour, while MPEG4-HD uses about 3.6GB/hour.
So, if your HR20 has a 300GB drive and has 12 hours of MPEG2-HD, it would have less free space than an HR21 with 18 hours of MPEG-4.

Even so, it seems like your space available numbers are goofy on both machines.
If it's really true that everything you're recording is HD (and not SD on a HD channel), then:
* The HR21 should have less than 75% available.
* The HR20 should have more than 51% available.