On 03/30/2013 12:28 PM, Tom Lane wrote:
Bruce Momjian <br...@momjian.us> writes:
On Sat, Mar 30, 2013 at 10:08:44PM +0800, 赖文豫 wrote:
As we know, SSDs are widely used in various kinds of applications. But the SMGR
in PostgreSQL still only
support magnetic disk. How do we make full use of SSDs to improve the
performance of PostgreSQL?
When the storage manager (SMGR) says magnetic disk, it is talking about
read/write media with random access capabillity, vs. something like
write-only media, which was originally supported in the code. Postgres
works just fine with SSDs; the only adjustment you might want to make
is to reduce random_page_cost.
To enlarge on that point: the current smgr layer is basically vestigial,
because the sorts of device dependencies the Berkeley guys envisioned
switching between are nowadays always handled at the filesystem and
kernel device driver layers. md.c is really an interface to the Unix
block device APIs; it has nothing whatsoever to do with whether the bits
are stored on spinning rust or something else.
This isn't the first time I've seen this sort of comment. Do we need to
add some wording like the above to the top of md.c and the README in
that directory?
cheers
andrew
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