| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Bruno Wolff III <bruno(at)wolff(dot)to> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Greg Stark <gsstark(at)mit(dot)edu>, Russell Smith <mr-russ(at)pws(dot)com(dot)au>, josh(at)agliodbs(dot)com, Postgres Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Checkpoint cost, looks like it is WAL/CRC |
| Date: | 2005-07-07 04:24:44 |
| Message-ID: | 3317.1120710284@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Bruno Wolff III <bruno(at)wolff(dot)to> writes:
> Are you sure about that? That would probably be the normal case, but are
> you promised that the hardware will write all of the sectors of a block
> in order?
I don't think you can possibly assume that. If the block crosses a
cylinder boundary then it's certainly an unsafe assumption, and even
within a cylinder (no seek required) I'm pretty sure that disk drives
have understood "write the next sector that passes under the heads"
for decades.
regards, tom lane
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