I have to add, the slave server is a bit sluggish at the command-line and
it didn't used to be that way.  load average is over 3 due to
processes blocked on I/O.

Looks like the system is I/O consists mainly of writing to disk ("bo"
blocks out in vmstat 1).

There is nothing on this system but postgres and slon.

I've asked the on-site IT guys to eye ball the server to make sure
there isn't a failed disk...

# vmstat 1
procs -----------memory---------- ---swap-- -----io---- --system--
-----cpu------
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 1  2    200  49656  51856 7659972    0    0   110   496   20   14  1
1 92  6  0
 0  3    200  49656  51856 7659972    0    0     0  7200 1910 1522  0
1 82 17  0
 0  3    200  49656  51856 7659972    0    0     0  6224 1738 1233  0
1 75 24  0
 0  3    200  49656  51856 7659972    0    0     0  6176 1741 1283  0
1 75 24  0
 0  3    200  49656  51856 7660092    0    0     0  6440 1957 1925  2
1 85 13  0
 0  0    200  53408  51892 7655436    0    0     0  3880 1749 2263  3
1 87  9  0
 0  0    200  53284  51892 7655716    0    0     0   284 1496 3169  6
1 92  0  0
 1  0    200  53036  51892 7656056    0    0     0   264 1516 3186  6
1 92  0  0
 0  0    200  52912  51892 7656336    0    0     0   272 1499 3222  7
1 92  0  0
 1  0    200  68288  51892 7641144    0    0     0   656 2045 3826  5
1 94  0  0
 0  2    200  67420  51892 7641888    0    0     0  6028 2330 3807  4
1 91  4  0
 1  0    200  67420  51900 7642220    0    0     0  5868 1908 1723  1
1 87 11  0
 0  0    200  66056  51900 7643764    0    0     0  1024 2136 4070  6
1 93  0  0
 0  0    200  64692  51904 7644780    0    0     0   736 2027 3776  5
1 94  0  0
 1  0    200  63204  51904 7646144    0    0     0   768 2086 3918  6
1 93  0  0
 0  3    200  61716  51904 7646824    0    0     0  3388 2177 3430  4
1 91  4  0
 0  5    200  61716  51904 7647092    0    0     0  6324 1738 1244  0
0 87 13  0
 0  3    200  61592  51904 7647092    0    0     0  6236 1727 1287  0
0 87 13  0
 0  4    200  61716  51904 7647100    0    0     0  7328 1861 1357  0
1 88 12  0
 0  4    200  61716  51904 7647100    0    0     0  7188 1852 1284  0
1 87 12  0
 0  3    200  61716  51904 7647164    0    0     0  6672 1804 1502  0
1 86 13  0
 0  3    200  61716  51908 7647160    0    0     0  6072 1725 1328  0
0 86 14  0
 0  3    200  61592  51908 7647224    0    0     0  6524 1877 1736  1
1 86 12  0
 0  3    200  61344  51908 7647224    0    0     0  6316 1894 1536  0
1 74 25  0
 0  3    200  61344  51908 7647496    0    0     0  6232 1724 1287  0
0 75 25  0
 0  2    200  61220  51916 7647488    0    0     0  6748 1887 1522  0
1 76 22  0
 0  0    200  61468  51924 7647600    0    0     0  4908 1824 1628  1
1 76 22  0
 0  0    200  61040  51924 7648280    0    0   144   648 1489 2794  4
1 95  1  0
 0  0    200  60916  51924 7648784    0    0     0   256 1443 2943  6
1 93  0  0
 0  0    200  60420  51924 7649124    0    0     0   248 1415 2805  5
1 94  0  0
 0  4    200  60172  51924 7649144    0    0     0  5612 1789 2176  2
1 87 10  0
 0  6    200  60172  51924 7649144    0    0     0  6988 1835 1320  0
1 87 12  0
 0  4    200  60172  51924 7649196    0    0     0  6488 1796 1498  0
1 81 18  0
 0  4    200  60172  51924 7649196    0    0     0  6424 1768 1462  1
1 75 23  0
 1  3    200  60048  51924 7649268    0    0     0  6704 1899 1616  0
1 75 24  0
 0  3    200  59428  51924 7649268    0    0     0  6968 1876 1404  0
1 74 25  0
 0  3    200  59676  51932 7649320    0    0     0  6344 1836 1640  1
1 80 18  0
 0  3    200  59676  51932 7649320    0    0     0  6400 1788 1241  0
1 88 12  0
 1  0    200  59924  51944 7649456    0    0     0   688 1469 2537  4
1 92  3  0