Docs PerformanceStatic » History » Revision 5
Revision 4 (moo, 2007-07-07 15:30) → Revision 5/7 (moo, 2007-07-07 15:30)
[[TracNav(DocsToc)]] h1. = Improving the Throughput of File Transfers = Jan has blogged about the development of async io and threaded stat() at http://blog.lighttpd.net/articles/tag/aio h2. == vmstat == <pre> $ vmstat 5 </pre> If you are using a threaded io-backend (e.g. gthread-aio) and see that the @`@b@`@ ``b`` column reaches the value of @`@server.max-read-threads@`@ ``server.max-read-threads`` you know that now all threads are waiting for the disk to respond. h2. == iostat == <pre> $ iostat -x 5 </pre> @`@r/s@`@ ``r/s`` is the number of requests per second which are handled by the disk. Due to the nature of hard-disks there is a upper limit you can get here: <pre> max-rps = (disk-rpm / 60) * 2 ((7200 rot/min) / (60 s/min)) * 2 seek/rot = 120 * 2 seek/rot = 240 seek/s </pre> For each request handle by the disk it has to do a seek. In the best case the next seek is just around the corner, in the worst case it just passed over the block to read and has to do a full rotation to get to the place again. On average this means it has to do half a rotation for a seek or 2 seeks per rotation. If you have more disks the max-rps sums up IF your data is well distributed over all disks. @`@util%@`@ ``util%`` of 100% means that the disk is either at the seek-limit (see r/s) or the throughput limit.