Blocksize is not the same as volume/partition/file size (http://en.wikipedia.org/wiki/Block_%28data_storage%29). A file system usually has a block size associated with it. In general terms, when data is pulled off the device it will usually pull off the whole block at the same time. Since related data is usually close by, the future accesses won't have to go back to this disk because that block is already cached in memory. The volume size is the product of the blocksize and the number of blocks.
Persistence works by creating a large file (casper-rw) with dd. The 2048 MB block size limit is a limitation of dd. Almost nobody would be using a block size that large, unless they are only working with large multi- gigabyte files of contiguous data. Using large blocks will be inefficient in most normal situations. This is why most filesystems default to a blocksize in the 1KB-4KB range. The fact that usb-creator is trying to create persistence files with an arbitrary block size is definitely a bug. Now as far as FAT32 is concerned it is capable of have larger than 2 GB volume sizes, but it does have a hard limit of 4 GB (2^32) for a single file. Usb-creator creates a file called casper-rw with dd and formats it to ext3. This file is mounted by ubuntu at boot time and is used to store persistent changes. However the casper-rw file is a single file saved on the FAT32 filesystem of the USB drive, and thus it cannot be larger than 4 GB. With the current blocksize bug in usb creator you will get an error about 'invalid blocksize' in your usb-creator log, but it will exit normally. If you fix usb-creator so that it uses a reasonable block size like 1 KB, then you will be able to go about 2048 MB without an error. However, if you go above 4 GB then you will run into the file size limitation of FAT32. You will see an error in your usb-creator log where it calls dd. It will write the file right up to 4 GB and then it will give some error about the wrong file size or out of space or something like that. The 4 GB limit is not a bug and is a technological limit of FAT32. Hopefully the patches in the bug report I linked to will get incorporated to make this clear to the user. -- No persistence with USB Creator in Ubuntu 8.10 https://bugs.launchpad.net/bugs/302485 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
