>
> Oh...I like this :) that would give us something that the "big
> guys" don't also, no? Bruce?
>
> Can someone clarify something for me? If, for example, we have
> the blocksize set to 16k, but the file system size is 8k, would the OS do
> both reads at the same time in order to get the full 16k? I hope someone
> can follow this through (unless I'm actually clear), but if we left the
> tuples size at 8k fixed, and had that 16k tuple span two rows, do we send
> a request to the OS for the one block, then, once we get that back,
> determine that we need the next and request that?
The filesystem block size really controls how fine-graned the file block
allocation is. It keeps 8k blocks as one contigious chunk on the disk
(ignoring trailing file fragments which are blocksize/8 in size).
How the OS does the disk requests is different. It is related to the
base size of a disk block(usually 512 bytes), and if multiple requests
can be sent to the drive at the same time(tagged queuing?). These are
really not related to the filesystem block size, except that larger
block sizes are made up of larger contigious disk block groups.
--
Bruce Momjian | 830 Blythe Avenue
maillist@candle.pha.pa.us | Drexel Hill, Pennsylvania 19026
+ If your life is a hard drive, | (610) 353-9879(w)
+ Christ can be your backup. | (610) 853-3000(h)