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Prompted by a question on DigitalSpy, I have checked the reserved disk space on my 1TB HDR-T2 and it is currently showing as 114GB which seems large. What is it used for?
Hi Martin,
I’ve done a little research on this subject, so here’s what I’ve been able to dig up so far.
For a start, the whole issue of actual disk size has been clouded by a clever sales ploy used by HDD manufacturers.
In software terms one kilobyte is equal to 1024 bytes.
In hardware terms (as used by HDD manufacturers) one kilobyte equals only 1000 bytes.
So for one gigabyte
Binary = 1,073,741,824
Decimal = 1,000,000,000
Difference = 73,741,824
or 6.8677% less !
For a drive with stated capacity of 500GB you really get only 465.66GB.
For one terabyte it gets even worse
Binary = 1,099,511,627,776
Decimal = 1,000,000,000,000
Difference = 99,511,627,776
or 9.095% less !
For a drive with stated capacity of 1000GB you really get only 909.05GB.
Looking under the bonnet of my 500Gb HDR T2 the Linux OS reports the file system partitions as follows:
Filesystem Size Used Available Use% Mounted on
/dev/sda1 1011.4M 35.4M 924.7M 4% /mnt/hd1
/dev/sda2 447.6G 66.3G 358.6G 16% /mnt/hd2
/dev/sda3 9.8G 261.2M 9.1G 3% /mnt/hd3
However, From the T2’s System Menu the disk space is reported like this:
Available 373.6 Gb
Used 74.0 Gb
Reserved 72.7 Gb
You can see that ‘Available’ plus ‘Used’ space totals 447.6Gb
This ties in nicely with what Linux says is the partition size of hd2.
Partition hd1 is 1Gb and is used for EPG data.
Partition hd2 is the main media storage area for recordings. It also contains the 13.5Gb live buffer file.
Partition hd3 is 9.8Gb and is used, as far as I can tell, as a cache for Portal content.
Just where Humax get the figure of 72.7Gb Reserved I have no idea.
What I do know is that it has no bearing whatsoever on the truth.
Raydon a bit off topic but can you clear up a point of confusion.
Is it GB or Gb. I ask because b normally seems to mean bit rather than byte as in bps (bits/sec). Same confusion with respect to mbps or is it Mbps.
This Wikipedia article uses gigabyte (with abbreviation GB) as 10^9 and gigibyte (with abbreviation GiB) as 2^30 and I think I am happy with that convention.
Thanks for the explanation on the disk usage.
grahamlthompson – 44 minutes ago »
Raydon a bit off topic but can you clear up a point of confusion.
Is it GB or Gb. I ask because b normally seems to mean bit rather than byte as in bps (bits/sec). Same confusion with respect to mbps or is it Mbps.
In the context of my post all references in to bytes (I don’t think I’ve ever seen HDD disk capacity referenced in bits. But you’re right, Bytes should be capital with a B. Please forgive my sloppy syntax
grahamlthompson – 1 hour ago » Same confusion with respect to mbps or is it Mbps.
lower case m usually denotes one thousandth (10^-3) whereas capital M is a Million (10^6) so mbps would be like splitting the atom 😉
raydon – 3 hours ago »
grahamlthompson – 44 minutes ago »
Raydon a bit off topic but can you clear up a point of confusion.
Is it GB or Gb. I ask because b normally seems to mean bit rather than byte as in bps (bits/sec). Same confusion with respect to mbps or is it Mbps.
In the context of my post all references in to bytes (I don’t think I’ve ever seen HDD disk capacity referenced in bits. But you’re right, Bytes should be capital with a B. Please forgive my sloppy syntax
Please don’t apologise I was sincerely confused. You see both around. As you must know I come from a heavy engineering background largely involving TW. or GW ( I hope that’s right
). In future I will use B for Byte and b for bit
grahamlthompson – 1 hour ago »
raydon – 3 hours ago »
grahamlthompson – 44 minutes ago »
Raydon a bit off topic but can you clear up a point of confusion.
Is it GB or Gb. I ask because b normally seems to mean bit rather than byte as in bps (bits/sec). Same confusion with respect to mbps or is it Mbps.
In the context of my post all references in to bytes (I don’t think I’ve ever seen HDD disk capacity referenced in bits. But you’re right, Bytes should be capital with a B. Please forgive my sloppy syntax
Please don’t apologise I was sincerely confused. You see both around. As you must know I come from a heavy engineering background largely involving TW. or GW ( I hope that’s right
). In future I will use B for Byte and b for bit Graham, I don’t believe for one minute you were confused. You were being pedantic for whatever reason I don’t care to imagine. I will edit the original post to clarify your confusion but I believe most readers will be able to interpret the original post without any clarification whatsoever.
I was being absolutely honest. If you look back at many of my posts you will find GB and Gb used randomly. Gb also seems to be used more often than GB even in specification listings. Thanks for the clarification
I was not intending to infer that the post was in in any way confusing, quite the reverse in fact.
O.K. thanks for clearing that up Graham. It seems though that I’m now unable to edit my original post.
Admins, is this lack of an edit facility intentional, or is the edit button just hidden in some obscure place. My eyesight is not as good as it used to be.
Hmmm. I can edit this post O.K. Is there a time limit on editing older posts ?
I wouldn’t bother Raydon as you said there’s no real possibility of confusion. You might like to post this info elsewhere to re-assure worried hdr-fox t2 users about their mythical reserved loss of storage
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I work with computer systems and the abbreviation of the ‘byte’ unit still confuses me! And now there is a convention for ‘real bytes’ with the KiB, MiB, etc…
The fact of the matter is that hard disk manufacturers have always (and will) used ‘Mega’, ‘Giga’ and ‘Tera’, etc. to denote multiples of 1000 ‘bytes’ for their storage devices they make.
Whereas, everyone else (operating systems, etc) with use these to denote multiples of 1024 ‘bytes’. This is where the discrepancy comes in… and confuses anyone who calculates disk space usage with reference to the ‘size’ of their hard disk drives!
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