Title: High IO Last modified: April 25, 2023 --- # High IO * Resolved [vermaakpetrus](https://wordpress.org/support/users/vermaakpetrus/) * (@vermaakpetrus) * [3 years, 2 months ago](https://wordpress.org/support/topic/high-io/) * Hi Till, * I am on a shared host (I think they use virtualization). They have recently enabled redis, but don’t really give any support. I do not have access to see the settings etc. * I run two websites, one on the domain and another on a subdomain. I use WP Super Cloudflare Cache. * I’ve installed the plugin and everything works, however sometimes the I/O maxes out and the sites freeze up for an hour or so. My databases are small around 36MB each. * Any idea to point me in the right direction? There seem to be more than enough memory. Viewing 8 replies - 1 through 8 (of 8 total) * Thread Starter [vermaakpetrus](https://wordpress.org/support/users/vermaakpetrus/) * (@vermaakpetrus) * [3 years, 2 months ago](https://wordpress.org/support/topic/high-io/#post-16684314) * For info, I have a hard limit of 5 MB I/O per second. It’s not a lot but as my sites are optimized, I never went above 3MB per second before enabling redis plugin. * Plugin Author [Till Krüss](https://wordpress.org/support/users/tillkruess/) * (@tillkruess) * [3 years, 2 months ago](https://wordpress.org/support/topic/high-io/#post-16685933) * Redis requires additional compute and memory to run, I’d suggest upgrading your account. Typically people run Redis on 2GB servers. it can be tight when only 1GB RAM is available. * I’ve never heard about I/O per sec as a limiting metric, what host are you using. * Thread Starter [vermaakpetrus](https://wordpress.org/support/users/vermaakpetrus/) * (@vermaakpetrus) * [3 years, 2 months ago](https://wordpress.org/support/topic/high-io/#post-16686835) * I am with sawebhosts.co.za. Definitely something weird is going on. Tried many many many times. In the end, it always results in high i/o. * Thread Starter [vermaakpetrus](https://wordpress.org/support/users/vermaakpetrus/) * (@vermaakpetrus) * [3 years, 2 months ago](https://wordpress.org/support/topic/high-io/#post-16688281) * I did a LOT of testing and found that this happens when turning it on for any two sites on one hosting package. I have a domain and subdomain; no matter what I do, it works with either as long as only one uses redis at a time. Specifying a DB or prefix does nothing to change this. I suspect it’s because the server uses virtualization. * So, the only option is to select which site must be accelerated and turn redis on there. I hope this helps anyone else on shared hosting that uses virtualization. * [@tillkruess](https://wordpress.org/support/users/tillkruess/) thanks for all the support!! * Plugin Author [Till Krüss](https://wordpress.org/support/users/tillkruess/) * (@tillkruess) * [3 years, 2 months ago](https://wordpress.org/support/topic/high-io/#post-16690151) * Thanks for the report. TBH it’s the first time I’ve heard that someone is restricted by I/O, typically people run a VPS with >2GB of memory. * Some sites use a lot more object cache keys and will thus transfer a lot more data. You can see the average cache size per page in the metrics under “Bytes”. * Thread Starter [vermaakpetrus](https://wordpress.org/support/users/vermaakpetrus/) * (@vermaakpetrus) * [3 years, 2 months ago](https://wordpress.org/support/topic/high-io/#post-16690311) * [@tillkruess](https://wordpress.org/support/users/tillkruess/), it’s not that it has high I/O. The hosting runs on cagefs virtualization, and cannot handle a domain and subdomain both using redis on that virtualized instance. It becomes screwy, and starts creating excessively high i/o. * With two sites, and only the one site on redis, the i/o is an average 400kb per second. But as soon as I switch on redis for both sites, the i/o is maxed out. I also start receiving random fatal WordPress errors, which goes away when I turn redis off an only let it run on one site at a time. And no, they are not sharing the same database. So, looks like cagefs cannot support redis for two sites on one virtualized instance. * Thread Starter [vermaakpetrus](https://wordpress.org/support/users/vermaakpetrus/) * (@vermaakpetrus) * [3 years, 2 months ago](https://wordpress.org/support/topic/high-io/#post-16692214) * Update: It’s working on both. There are two php versions available on a virtualized instance, alt-php (provided by CloudLinux) & ea-php (shipped by cPanel).I was using ea-php which cannot work with two redis on one instance. I switched to alt-php and everything is happy happy happy! * Plugin Author [Till Krüss](https://wordpress.org/support/users/tillkruess/) * (@tillkruess) * [3 years, 2 months ago](https://wordpress.org/support/topic/high-io/#post-16693260) * Nice! Viewing 8 replies - 1 through 8 (of 8 total) The topic ‘High IO’ is closed to new replies. * ![](https://ps.w.org/redis-cache/assets/icon-256x256.gif?rev=2568513) * [Redis Object Cache](https://wordpress.org/plugins/redis-cache/) * [Support Threads](https://wordpress.org/support/plugin/redis-cache/) * [Active Topics](https://wordpress.org/support/plugin/redis-cache/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/redis-cache/unresolved/) * [Reviews](https://wordpress.org/support/plugin/redis-cache/reviews/) * 12 replies * 2 participants * Last reply from: [Till Krüss](https://wordpress.org/support/users/tillkruess/) * Last activity: [3 years, 2 months ago](https://wordpress.org/support/topic/high-io/#post-16693260) * Status: resolved