Quote:
Originally Posted by
rarino2
Hi Jim! Thanks for your time.
I'm not sure to understand you well. When you say "blocks" in your post, are you speaking about physical (disk) blocks (sectors)?
!
A block is still (on most FS) refers to 4K of data only.
On most system the page-cache is still of this fix sizes. Hence on all block I/O is of 4K or less. The file systems on such system utilizes the maximum size which is 4k.
However, if you see the disk architecture, they have been under trial by various vendors with various sector sizes; with 512bytes sector disk supported by most of the File system and storage product vendors (they however support various other size disks too -but 512b sector disk is in most common use probably because windows/DOS/UNIX FS supported them).
In order to support various disk architecture and FS supporting them use fragmentation which of course let you divide the 4k of page size into various fragments of 1, 2, ... 8 fragments per page.
8-fragments per page is the lowest value which translate into the size of a sector. You can of course not use a sector half of it. For I/O of 1 to full 512 byte of data a full sector gets used in one disk write.
Can you post here the steps you used to test this figures :
1) On UFS, how you saw the fragment size of 1 KB?
2) How did you looked at the 512kb I/O ?