On Fri, Jan 31, 2014 at 8:21 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > So on a filesystem that supports "holes" > in files, I'd expect that the added segments would be fully allocated > if XLogReadBufferExtended did the deed, but they'd be quite small if > _mdfd_getseg did so. The du results you started with suggest that the > former is the case, but could you verify that the filesystem this is > on supports holes and that du will report only the actually allocated > space when there's a hole?
Yup, it's xfs: # dd if=/dev/zero seek=1M count=1 bs=1kB of=hole 1+0 records in 1+0 records out 1000 bytes (1.0 kB) copied, 5.7286e-05 s, 17.5 MB/s # ls -ls hole 4 -rw-r--r-- 1 root root 1048577000 Feb 1 09:35 hole # ls -ls 1261982.5* 1048576 -rw------- 1 ua8157t9mbut8r postgres 1073741824 Jan 14 12:51 1261982.5 1048576 -rw------- 1 ua8157t9mbut8r postgres 1073741824 Jan 23 02:05 1261982.50 1048576 -rw------- 1 ua8157t9mbut8r postgres 1073741824 Jan 23 02:07 1261982.51 1048576 -rw------- 1 ua8157t9mbut8r postgres 1073741824 Jan 23 02:09 1261982.52 1048576 -rw------- 1 ua8157t9mbut8r postgres 1073741824 Jan 23 02:10 1261982.53 508680 -rw------- 1 ua8157t9mbut8r postgres 520888320 Jan 23 02:12 1261982.54 -- greg -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
