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Old 24 October 2017, 19:18   #2
thomas
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Join Date: Jan 2002
Location: Germany
Posts: 5,781
Quote:
What is this identifier exactly, and what does it do?
The identifier is the unique key of the file system in Filesystem.resource. There can be only one file system with the same identifier in the system. The identifier also selects the file system for a partition. Like the one-byte partition type on a PC you have a 4-byte partition type on the Amiga. The main difference is that PC's partition types are well defined while on the Amiga you can freely choose the identifier.


Quote:
One of the options here is called "Mask". I understand what a bitmask is and what it does. But what is its application here?
By the mask a file system can decide whether the device driver is able to do DMA from a buffer or not. If the start address of the buffer fits the mask, then the buffer can be used for DMA, otherwise the file system has to allocate a new buffer and copy the contents there.

Quote:
Another setting is called "Max Transfer". I understand I should set it to
0x0001FE00. Why? What does this do?
The MaxTransfer value defines the largest amount of data which can be sent over the bus in one chunk. Like MTU in networking. Normally a device driver should be able to deal with any chunk sizes. Too big buffers have to be split into several transfers. But if the implementation is buggy, you can let the file system do the split by specifying a small MaxTransfer.

0x1fe00 is 255 times 512. The ATA bus can transfer a maximum of 256 blocks of 512 bytes. This would be 0x20000. One reduces the value by one block for safety.


Quote:
Regarding file system block size, I always set it to 512. But what are the pros and cons to other settings here?
Generally larger blocks are faster but waste more space.

If the file system limits the partition size by a maximum number of blocks, you can also increase the partition size limit by specifying larger blocks.

Especially when it comes to flash memory and SSDs it might be a good idea to align file system blocks to physical sectors.
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