[OSM-dev] Dev is going to burn soon

Sebastian Spaeth Sebastian at SSpaeth.de
Mon May 14 10:12:03 BST 2007


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Sebastian Spaeth wrote:
> Tile serving from dev has nearly come to a halt. the munin cpuusage stat
> shows iowait at 87% and load at 6.

Let me put forward an alternative theory of why that happens:
So far we focused on hdc (the tile storage) and waited for hdd to
provide relieve.

But looking at the IOStats on munin (remote diagnosis like that is to be
bound to be a little crytal ball watching):

IOStat (blocks per second read/write):

Disk	Read	Write
hdc	68	0
hdd	33	396
hda	499	2.2k
- ---------------------
Total	600	2.6k

Ouch, it seems that actually hda is bearing the lions share of all reads
(ca 83%) and writes (ca 84%). Ouch. How can that be? Apache log file
entries being written for everything? Plus a MySQL log file entry
written for everything? It looks like we have to give hda actually some
relieve here. How full is hda, really?

Just shooting in the dark, of course. Hope it helps someone.

Spaetz
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