HFS+ can have files up to 2^63 bytes, but a volume can only have 2^32 blocks. You really don't want blocks to be any bigger than 8KB (2^13), which means you could only support one 2^45 byte file. XFS and BFS allow much larger volumes and files IIRC.
The operating system allocates disk space in what are called blocks, and it numbers each block. So, a file on your system tells which block(s) are occupied for a certain data file. Now, a filing system has a limit for the number of blocks it can identify, so for that reason, there is not a set size for each block. The trouble comes from very big hard drives, where the smallest block would be a sizable amount. (On a 500 GB Hard Drive, there would be 500,000,000,000*8 bits / 2^32 allocation blocks = 14 Bytes/block. On The old HFS, which was 16 bit, 500,000,000,000*8 bits / 2^16 allocation blocks = 953 KB/block. You can see how this could be a problem, but it really doesn't look like there would be that big of an advantage for a 64 bit allocation space.
The operating system allocates disk space in what are called blocks, and it numbers each block. So, a file on your system tells which block(s) are occupied for a certain data file. Now, a filing system has a limit for the number of blocks it can identify, so for that reason, there is not a set size for each block. The trouble comes from very big hard drives, where the smallest block would be a sizable amount. (On a 500 GB Hard Drive, there would be 500,000,000,000*8 bits / 2^32 allocation blocks = 14 Bytes/block. On The old HFS, which was 16 bit, 500,000,000,000*8 bits / 2^16 allocation blocks = 953 KB/block. You can see how this could be a problem, but it really doesn't look like there would be that big of an advantage for a 64 bit allocation space.
How, assuming WMF is right, do XFS and BeOS allow bigger volumes? Is it just a bigger block size?
Comments
Originally posted by Spartacus
Will the 64 bit filesystem, like the one found in BeOS, be present in 10.4. I didn't heard about it for Panther.
HFS+ already allows pretty large files, but there will be no new filesystem for Panther.
Do a 64 bit filesystem a better thing for a 64 bit processor than a 32 bit processor or do it have no consequences?
It doesn't matter.
http://developer.apple.com/technotes/tn/tn1150.html
Originally posted by FotNS
He didn't state that, and HFS is not 64 bit.
it can handle files that are 2^63 bits in length, what else do you want?
Originally posted by bauman
The operating system allocates disk space in what are called blocks, and it numbers each block. So, a file on your system tells which block(s) are occupied for a certain data file. Now, a filing system has a limit for the number of blocks it can identify, so for that reason, there is not a set size for each block. The trouble comes from very big hard drives, where the smallest block would be a sizable amount. (On a 500 GB Hard Drive, there would be 500,000,000,000*8 bits / 2^32 allocation blocks = 14 Bytes/block. On The old HFS, which was 16 bit, 500,000,000,000*8 bits / 2^16 allocation blocks = 953 KB/block. You can see how this could be a problem, but it really doesn't look like there would be that big of an advantage for a 64 bit allocation space.
How, assuming WMF is right, do XFS and BeOS allow bigger volumes? Is it just a bigger block size?
Originally posted by Whisper
How, assuming WMF is right, do XFS and BeOS allow bigger volumes? Is it just a bigger block size?
Bigger blocks are bad. IIRC, XFS and BFS allow 2^64 blocks per volume.
Originally posted by wmf
Bigger blocks are bad. IIRC, XFS and BFS allow 2^64 blocks per volume.
So all filesystems use blocks and it's just a question of how many and how big?
Originally posted by Whisper
So all filesystems use blocks and it's just a question of how many and how big?
Yes, but there are plenty of other factors that influence performance and reliability.
Originally posted by wmf
Yes, but there are plenty of other factors that influence performance and reliability.
Like what? Is there a good website I can go to that explains all of this so you don't have to type it out?
Originally posted by Whisper
Like what? Is there a good website I can go to that explains all of this so you don't have to type it out?
I would recommend a good operating systems textbook, Dominic's book, and the XFS and JFS papers.
http://www.amazon.com/exec/obidos/tg...96653?v=glance
http://oss.sgi.com/projects/xfs/pape...nix/index.html
http://www-106.ibm.com/developerwork...ary/l-jfs.html
Originally posted by wmf
I would recommend a good operating systems textbook, Dominic's book, and the XFS and JFS papers.
http://www.amazon.com/exec/obidos/tg...96653?v=glance
http://oss.sgi.com/projects/xfs/pape...nix/index.html
http://www-106.ibm.com/developerwork...ary/l-jfs.html
Cool, thanks, I'll check them out