Bruce Momjian <bruce@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.
regards, tom lane