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Raw Filesystem type
- Thread starter bahija
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If UNIX, you have "raw/block" and "cooked/cooked". A raw logical volume is one that does not have all of the overhead required for standard JFS filesystems. Indeed, data is written directly to the logical volume, and no jfs before or after image logging is done. The jfs before/after image logging is how the system is able to recover in the event of a crash.
When you write data to a jfs filesystem, just before AIX does the write, the "jfslog" takes an image of the data. Your data is then written, and another image is taken. If the LVM does not get a good response back from the "after" image, it rolls the data back to the before image, and returns an error to your program.
In a "raw" logical volume, none of this is done. You write it and it is done, providing there is no other exceptions. Raw logical volumes can be faster than JFS write, because all of the assiciated JFSLOG I/O is not done.
Bill.
When you write data to a jfs filesystem, just before AIX does the write, the "jfslog" takes an image of the data. Your data is then written, and another image is taken. If the LVM does not get a good response back from the "after" image, it rolls the data back to the before image, and returns an error to your program.
In a "raw" logical volume, none of this is done. You write it and it is done, providing there is no other exceptions. Raw logical volumes can be faster than JFS write, because all of the assiciated JFSLOG I/O is not done.
Bill.
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