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litespeed_wiki:ttfb [2018/11/12 16:40] Erwin Venekamp [Insufficient caching] |
litespeed_wiki:ttfb [2018/11/12 16:43] (current) Erwin Venekamp [Slow servers] |
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| ===== ModSecurity ===== | ===== ModSecurity ===== | ||
| - | Sometimes, having a large number of ModSecurity rules, or very complex ones, can lead to a significant rise in TTFB. This is particularly true with the ''SecRequestBodyAccess On'' directive. When diagnosing high TTFB issues, you may want to temporarily disable ModSecurity, to rule this possibility out. | + | Sometimes, having a large number of ModSecurity rules, or very complex ones, can lead to a significant rise in TTFB. This is particularly true with the ''SecRequestBodyAccess On'' directive, and rulesets that use RBL DNS lookups for requests. When diagnosing high TTFB issues, you may want to temporarily disable ModSecurity, to rule this possibility out. |
| ===== Slow DNS ===== | ===== Slow DNS ===== | ||
| Rarely, a slow DNS server may be responsible for a high TTFB, especially in artificial benchmarks, where DNS is not cached. Several websites are available to test the speed of your site's DNS response, such as https://www.dnsperf.com/dns-speed-benchmark | Rarely, a slow DNS server may be responsible for a high TTFB, especially in artificial benchmarks, where DNS is not cached. Several websites are available to test the speed of your site's DNS response, such as https://www.dnsperf.com/dns-speed-benchmark | ||
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| ===== Slow servers ===== | ===== Slow servers ===== | ||
| - | This is especially common in VPSes, where some providers severely oversell, or use old setups. You may also encounter this if your server uses very old, very slow hardware, such as underpowered processors, or processors that do not support hardware AES acceleration. You may need to migrate to another provider. | + | This is especially common in VPSes, where some providers severely oversell, or use old setups. You may also encounter this if your server uses very old, very slow hardware, such as underpowered processors, or processors that do not support hardware AES acceleration. If this is the case, you will likely benefit from migrating to another provider. |