On 5/11/06, Peter Rival <[EMAIL PROTECTED]> wrote:
Richard Elling wrote:
> Oracle will zero-fill the tablespace with 128kByte iops -- it is not
> sparse. I've got a scar. Has this changed in the past few years?
Multiple parallel tablespace creates is usually a big pain point for
filesystem / cache interaction, and also fragmentation once in a while. The
latter ZFS should take care of; the former, well, I dunno.
The purpose of zero-filled tablespace is to prevent fragmentation by
future writes, in the case when multiple tablespaces are being
updated/filled on the same disk, correct?
This becomes pointless on ZFS, since it never overwrites the same
pre-allocated block, i.e. the tablespace becomes fragmented in that
case no matter what.
Also, in order to write a partial update to a new block, zfs needs the
rest of the orignal block, hence the notion by Roch:
"partial writes to blocks that are not in cache are much slower than
writes to blocks that are."
Fortunately I think DB almost always does aligned full block I/O, or
is that right?
Tao
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