February 2020 - Arch-mirrors - lists.archlinux.org

[arch-mirrors] CDN based/caching mirror?
by Kristian Klausen 04 Mar '20

04 Mar '20

Hi I'm considering setting up a Arch Linux mirror and I'm considering a different design. So instead of mirroring the whole thing, the idea is to mirror only the database files (core.db etc) and download the packages on demand from a Tier 1 mirror (and let nginx cache them). By doing it that way, I only download requested packages from the Tier 1 mirrors, instead of downloading the whole thing (saving Tier 1 bandwidth). To provide even better performance a CDN (ex: Cloudflare) could be used to provide more caching. So we end up with a setup like this: Cloudflare -> Nginx cache -> Tier1 mirrors (nginx with multiple upstream) Do I miss something? Is this a bad idea? If I do setup a mirror like that, is there any chance it could be added as a official mirror? Best regards Kristian Klausen

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[arch-mirrors] Changes to archmirror.lavatech.top
by Ave 13 Feb '20

13 Feb '20

Hello, I'm the sysadmin of archmirror.lavatech.top. I moved archmirror.lavatech.top's rsync source to mirror.pseudoform.org as f4st.host seems to be having issues (it didn't get updates in ~9 days) and is giving 502 on the main page. -Ave Ozkal

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Re: [arch-mirrors] [sysadmin] CDN based/caching mirror?
by Kristian Klausen 03 Feb '20

03 Feb '20

On 30.01.2020 17.04, Konstantin Ryabitsev wrote: > On Sun, 26 Jan 2020 at 11:19, Kristian Klausen via arch-mirrors > <arch-mirrors(a)archlinux.org> wrote: >> I'm considering setting up a Arch Linux mirror and I'm considering a >> different design. >> >> So instead of mirroring the whole thing, the idea is to mirror only the >> database files (core.db etc) and download the packages on demand from a >> Tier 1 mirror (and let nginx cache them). By doing it that way, I only >> download requested packages from the Tier 1 mirrors, instead of >> downloading the whole thing (saving Tier 1 bandwidth). >> >> To provide even better performance a CDN (ex: Cloudflare) could be used >> to provide more caching. So we end up with a setup like this: >> Cloudflare -> Nginx cache -> Tier1 mirrors (nginx with multiple upstream) >> >> Do I miss something? Is this a bad idea? > If you are trying to save Tier1 some bandwidth, you'll probably > actually end up causing them more problems due to increased random > seek waits. Tier1 mirrors may not necessarily have fast storage -- for > example, all kernel.org mirror nodes have terabytes of spinning rust > and about half-a-TB of ssd used via lvm-cache. It works great for > Tier1 setups because most Tier2 mirrors want the same set of recent > updates that are served out of ssd cache. If a new mirror comes along > and wants to slurp and entire distro, that is fine too, because even > if there's higher iowait latency, the Tier2 mirror isn't working > against any HTTP timeouts or impatient clients and doesn't care if the > data arrives at a slower rate due to higher iowait. Tier1 can also > tell Tier2 mirror "I'm overloaded right now, please try again later" > and it'll be fine as most Tier2 mirrors can wait an hour or two before > receiving updates. > > Making Tier1 mirrors a "cold cache" for your setup will likely cause > more disk thrash for them, but will also result in poorer service for > people using your mirror due to the reasons I listed above. Tier 1 mirrors is also used directly by end-users (correct me if I'm wrong) So worst-case (cache miss) my SSD-backed shared cache won't be noticeable slower than pulling directly from the Tier 1 mirror. Best-case (cache hit) I'm saving the Tier 1 mirror some bandwidth and disk usage. My idea is basically tiered caching (CDN -> Nginx SSD-backed shared cache -> Tier 1 mirror(s)), is that worse than status quo? :) > If someone > tries to install a package and watches their download bar sit at 0 for > half a minute due to backend proxies fetching data from Tier1 origin, > that's going to result in frustrated people. Nginx streams the data as it is received from the upstream server, so worst-case (cache miss) the data can be delivered as fast as received from the upstream server. > TL;DR: If you can afford CDN-fronting your mirror, that should be > mostly fine, but I would recommend against using Tier1 as your > cache-miss backend. Storage is cheap and most Tier1 mirrors have > unlimited bandwidth, so just run a Tier2 mirror (with slow/fast > storage caching) and keep local copies of everything. > > -K > (mirrors.kernel.org administrator)

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