Gacek's questions

I have a dedicated server running on subdomain. I want to configure subdomains as DNS. Basically, I use example.com as my main company domain. I will, probably have more than one dedicated server and want them to be s1, s2 etc.

I redirected server.example.com to another DNS provider via NS entries
server.example.com NS ns1.hostingcompany.example.com
server.example.com NS ns2.hostingcompany.example.com

And there I setup following entries:

servers.example.com     NS  ns1.hostingcompany.example.com.
servers.example.com     NS  ns2.hostingcompany.example.com.

s1.servers.example.com  NS  ns1s1.servers.example.com.
s1.servers.example.com  NS  ns2s1.servers.example.com.
ns1s1.servers.example.com   A   192.0.2.1
ns2s1.servers.example.com   A   192.0.2.2
s1.servers.example.com  A   192.0.2.1

But, servers.example.com does not have A record. I skipped it, as I wanted only to use it as grouping DNS entry.

Everything seems to work, except my local bind server in company. It does not recognize s1.servers.example.com and any of subdomains. When I switch to google DNS it seems to work fine.

Question is, if this setup is proper and will work?

Note: Maybe I don't understand how NS entries work, as far as I understand is when NS server exists in domain entry, pointing to other DNS server it's considered "Don't ask me, ask another server" and A records are not needed in this chain.

I have a server, which has 12 Cores, and usage is 42. What does it mean?

As far as I know 1 i 100% of one core. So 42 is 100% of 42 cores?

Not sure what it is, but everytime I try to run one http request from browser, second must wait for first to fisnish. Is it server side configuration/seciurirty?

For example, I have 2 files long.php and short.php. After making request to long.php one I totally cannot open short.php. After long.php is finished, short.php is then loaded.

Not sure what it is related to. It does not happen for short scripts... only big ones. Maybe one IP user can open one connection to database etc?

EDIT:
Great example of how to "reproduce" this is to install XAMPP, start import of database on one browser. During that time, I cannot open another phpMyAdmin tab and work. Have to open different browser and then can work normally.

Firefox Tab 1: Imporing database with phpmyadmin
Firefox Tab 2: Opening phpmyadmin waits untill Tab 1 finishes
Chrome Tab 1: Works without problems or delays.

My working server crashed, more precise, my HDD got bad sectors.
What is proper method to make a backup from non-working server and restore it later on newly installed server?

Any set of files I need to copy/replace?

I found this, but I don't think it answears my question: Is it safe to assume that two hosts on the same /24 network belong to the same AS-number?

I have online shop, on which somone is spamming massievely shopping carts. That IP belongs to a company which I found by using who.is https://who.is/whois-ip/ip-address/38.99.82.254

It states that their IP network is: network:IP-Network:38.99.82.0/24

Is it safe to assume that this network belongs to this company? So if I block by this IP mask I don't block some kind of legit ISP?

If no, then is there a way to determine what IP range should I block from this IP?

There are few different php "wrappers"(?). What are differences between them? Tried to google some, but cant seem to find informations. (mod-php is not googleable).

Why might I choose one over another?