bug#46942: ci.guix.gnu.org is slow from my system

[raid5atemyhomework]

Hi zimoun,

> Hi,
>
> On Fri, 05 Mar 2021 at 14:46, raid5atemyhomework 
> raid5atemyhomework@protonmail.com wrote:
>
> > Are there any other mirror substitute servers aside from `ci.guix.gnu.org`?
>
> Well, only one in China I AFAIK.
>
> https://mirrors.sjtug.sjtu.edu.cn/guix
>
> Seehttps://yhetil.org/guix/87czz24ilu.fsf@riseup.net for details.


Thank you very much, an experimental `wget` shows I get much higher speeds from 
this:

```
$ wget 
https://mirror.sjtu.edu.cn/guix/nar/lzip/1bdldr80p39g1mjnh76xw6hmwqrrb8lz-wine64-6.0
--2021-03-06 06:45:10--  
https://mirror.sjtu.edu.cn/guix/nar/lzip/1bdldr80p39g1mjnh76xw6hmwqrrb8lz-wine64-6.0
Resolving mirror.sjtu.edu.cn (mirror.sjtu.edu.cn)... 111.186.58.212, 
2001:da8:8000:7100::322:a
Connecting to mirror.sjtu.edu.cn (mirror.sjtu.edu.cn)|111.186.58.212|:443... 
connected.
HTTP request sent, awaiting response... 200 OK
Length: 57048561 (54M) [application/octet-stream]
Saving to: ‘1bdldr80p39g1mjnh76xw6hmwqrrb8lz-wine64-6.0.3’

1bdldr80p39g1mjnh76xw6hmwqrrb8lz-wine64-6.0.3   
100%[=====================================================================================================>]
  54.41M  3.82MB/s    in 17s

2021-03-06 06:45:31 (3.21 MB/s) - 
‘1bdldr80p39g1mjnh76xw6hmwqrrb8lz-wine64-6.0.3’ saved [57048561/57048561]

```

I will try it out as the first server in `--substitute-urls`.

Would it not be appropriate to somehow put a list of such substitute servers 
(even if it is currently only a single mirror) somewhere official, like the 
Guix manual? I suppose if Peng Mei Yu thinks this mirror would be maintained 
long term?

Thanks
raid5atemyhomework