Sporadically slow MyISAM inserts

MySQL & MariaDB Other MySQL® Questions
1

I have a simple MyISAM table (8 fields; 22 bytes per row plus c. 40 bytes of index per row). Currently, the table has several million rows - and I run frequent bulk inserts, each of a few few hundred thousand rows. Typically, it inserts c. 5000 rows per second, but occasionally a row takes 5-60 seconds to insert. This happens perhaps every 2,000-20,000 rows or so. I notice that the IO wait in Linux ‘top’ command can go as high as 90% during the insert process, so guess it’s to do with disk writing. Is there any buffer which could help?
Thanks!

2

It could be flushing key buffer or simply dirty pages from MYD file.

3

Thanks Peter

Would there be anything which would identify which of these it was, or how would you fix it?

Alternatively - someone at Rackspace suggested that it might be rebuilding the indexes. Would that sound likely?

Many thanks again!