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Virtual Server - Frequently asked questions

The following are commonly asked questions about our Virtual Server services:

Categories
Virtual Server Basics
Compatibility Issues
Hardware Allocation
Installed Packages
Network Configuration
Using The MirroredHosting.com companion account
Network Traffic
Backups
Administration
 
Virtual Server Basics
Q:
How do virtual servers work?
A:

A virtual server is a separate Linux computer that runs as a guest of a physical Linux computer. Each virtual server is a complete Linux system including a kernel, RAM, swap, disk, and installed packages.

Q:
Which virtual server code are you using?
A:

We run User-mode Linux in "SKAS" (Separate Kernel Address Space) mode. To further enhance security, we run our virtual servers in "chroot jail's".

 
Compatibility Issues
Q:
How compatible are your virtual servers?
A:

Incredibly. With the exception of hardware access, you can do just about everything in a virtual server that does not require modifications to the kernel. All of the services that we supply on the Internet are actually running production inside of UML virtuals. These include production web services, database servers for admin functions, e-mail, etc.

Q:
What version of Linux are your virtual servers running?
A:

Our virtual servers have Redhat 7.3 installed running on a stock, kernel.org, 2.4.20 kernel.

Q:
I'm not really root, am I?
A:

Yes you are. User-mode Linux is a complete Linux computer running as a guest task on the underlying host system. When you are root, you are really root with a UID of 0 running standard libs, etc. This is why you can use virtual Linux servers anywhere you would use a standard, dedicated, Linux server.

 
Hardware Allocation
Q:
How much RAM does my system have?
A:

We configure systems with "virtual RAM" sizes ranging from 32 Megabytes to about 490 Megabytes (this is the limit in "non hi-mem" mode for User-mode-linux).

Q:
How much SWAP does my system have?
A:

This depends on the hosting plan that you have selected. On most plans we configure a swap partition that is equal in size to your RAM size. With some configurations, the swap file is twice as large.

Q:
How are my partitions setup?
A:

Standard virtual systems have two partitions. Partition 0 contains an "ext3" formatted filesystem that is the root filesystem for your virtual system. Partition 1 is a swap partition.

Q:
Can I get additional partition space?
A:

If you are running one of our small, low-cost servers, no. If you need more space, you will need to move to a larger hosting plan. Of course, with virtual servers, this is really quite easy technically.

For our larger servers, we can configure an additional Linux partition within the virtual server. This partition is then setup so that it is sub-managed within the virtual system with LVM (Linux Volume Manager). Thus you can then create multiple volumes, do snapshot backups, etc. The additional LVM volumes can be formatted ext2, ext3, reiserfs, or left as "bare" partitions for database use.

Q:
Do you overcommit resources?
A:

No. We are very careful to configure system with adequate resources (particularly RAM) to host the virtuals that reside on a physical host. For example, if we have 20, 32Meg virtuals, this would require 640Meg of physical memory. We would run these 20 virtuals on a host system with 1 Gigabyte of RAM giving each virtual it's own, essentially dedicated, memory.

Q:
How many virtuals are there on a host?
A: This depends on the size of the virtuals, but at most 20. With some large virtual configurations, this might be as low as 2 (or even 1).
Q:
What is the host hardware configuration?
A: Each host is a rackmount system with an AMD XP2000+ (or faster) processor, 1 Gigabyte of RAM, and RAID-1 mirrored hard drives. They are connected to the Internet via gigabit and/or 100 megabit switched ethernet.
   
Installed Packages
Q:
Which Linux packages are installed?
A: Almost everything. Basically we install everything that is not related to X-windows and minus a few documentation directories (to save space). All in all there are 411 packages installed occupying about 1 Gigabyte of space.
Q:
What tools and languages can I use?
A: Just about everything is already installed. This includes Apache, perl, PHP, Python, OpenSSL, MySQL, C, C++, Java, curl, webmin, etc. Because the system is yours, you can also install additional packages including CPAN updates, commercial databases like U2 and Oracle, etc.
   
Network Configuration
Q:
Do I have a public IP address?
A: The "eth0" device of your virtual server has a real, public, IP address that is directly connected to a high-speed Internet backbone from one of our providers. Your network connection is actually "pre-filtered" so that you don't get all of the usual junk that exists in Internet data centers (you won't see Netbios broadcast packages for example), but yours is a real, static IP address that you can run any service on.
Q:
Can I get additional IP address?
A: Yes, but we discourage this. The Internet is running out of IP addresses and it is important that users conserve them whenever possible. Most Internet services like web and mail can host many domains on a single IP address and we highly recommend this. If you really need a separate IP address, we can supply you with this, but there is a setup and monthly fee.
Q:
How is the firewall setup?
A:

Your system comes with a default firewall based on the "iptables" package. This firewall restricts inbound connections to:

  • ssh
  • http
  • https
  • ftp
  • webmin

and outbound connections to:

  • ssh
  • domain

This firewall is typically so restrictive that even if your system is compromised, most Internet worms will not know how to "phone home".

You have complete control over the firewall and can open any communication port that you wish (or delete the firewall entirely if desired).

Q:
How does your "MultiPath" connectivity work?
A:

All of our datacenters have Internet connections to multiple providers. Each provider assigns us a block of IP addresses on their networks. We make these addresses available to your virtual server in a number of way.

Backup path for ssh - We supply you with a free backup IP address that you can SSH to to access your server. This SSH access uses a nonstandard TCP port number (it is not port 22) but is otherwise a full-bandwidth connection to your server.

MultiPath http/https - We give you a free mirroredhosting.com account including MultiPath web services. Within this account, you can setup directory mount points that "reverse-proxy" requests into your virtual server.

MultiPath e-mail - Your mirroredhosting.com account also includes e-mail services allowing you to receive and forward e-mails into your virtual server on a domain-by-domain or user-by-user basis.

   
Using The MirroredHosting.com companion account
Q:
Why should I use the companion MirroredHosting.com account with my virtual service?
A:

There are a number of reasons for this:

  • Many services are already setup and are easier to use than running them inside of your virtual.
  • Standard services like static-content HTTP, DNS, and EMAIL are more efficient and take fewer system resources than running a separate copy of these within your virtual.
  • Services running in MirroredHosting.com don't slow down your virtual or use resources from your virtual.
  • Services running in MirroredHosting.com are "better" than what you are likely to setup on your virtual server:
    • Apache is tuned for maximum performance
    • DNS services are replicated across five servers at multiple locations
    • E-mail is full-featured with unlimited mailboxes, POP3, IMAP, WebMail, and optional virus/spam filtering.
    • Look over the MirroredHosting.com FAQ for more information.
  • The MirroredHosting.com services are more reliable because they are running on mirrored servers with redundant Internet connections.
  • You can use any amount of space that you need in MirroredHosting.com without "disk full" messages. Space over the 100 Megabytes allocated is billed at $1/25Megabytes ($40/Gig).
Q:
What is your design philosophy regarding MirroredHosting.com services vs. MirroredServer.com virtual servers?
A:

We believe that the two are extremely complimentary to each other. Basically, we recommend that you run the following functions inside of your MirroredHosting.com account:

  • DNS
  • Static HTTP and HTTP web pages
  • EMAIL

And run all of your dynamic application code inside of your virtual.

Q:
How can I mix static and dynamic web pages when I use my MirroredHosting.com companion account?
A:

The MirroredHosting.com admin application lets you "proxy" web directories within any domain. A "proxy" is where the web server acts as a relay and passes the transaction through to a second web server. The second web server in this case is your virtual server.

You set this up by defining a "proxy directory" such as:

Proxy: http://www.mydomain.com/app ==> http://v-2374.easyco.net/

Requests from the public directed to the /app directory in the www.mydomain.com domain name will actually be serviced by the web server running on your virtual system. The presence of your virtual server is completely transparent and hidden from the user (this is a proxy, and not a redirect). Because the user is communicating with our mirrored servers, they get the advantage of MultiPath and server mirroring.

Another advantage of this is that it lets you take your virtual server application down (lets say you need to do some programming) while still leaving you with a static web site so that your users can still get to your content.

   
Network Traffic
Q:
How do you measure network usage?
A:

We monitor packet transmissions every minute on our side of your network interface. This allows us to count bytes directly "on-wire".

Q:
How much Internet transfer do I get?
A:

Various hosting plans differ, but all get at least 5 Gigabit (which is quite a lot).

Q:
What if I go over my transfer allocation?
A:

Additional transfer varies with the hosting plan, but starts at only $5/Gigabyte.

   
Backups
Q:
Do you backup my system?
A: With most hosting accounts, Yes. Many virtual server account come with an included "backup plan". All virtual server accounts have this as an option. If you don't have us backing up your server, you should definitely do it yourself. Backup plans also include options for "local", "remote", and "mirrored" backups.
Q:
What is a "local" backup?
A:

With local backups, we have a process that nightly makes a complete save of your system and saves this on a separate computer system located in the same facility as your virtual server. Backups are automatically rotated and you have two choices:

  • Standard - keep the last 2 days plus the last 2 end-of-week saves.
  • Enhanced - keep the last 3 days, the last 4 end-of-week, and the last 3 end-of-month saves.
Q:
What is a "remote" backup?
A: A remote backup is performed in addition to your local backup. In this case we take the local backup and copy it to another computer system that is in a different facility. Remote backups can be performed monthly, weekly, or even daily. Different plans have different retention policies, but most users remote backup monthly or weekly and keep the last two backups on-line.
Q:
What is a "mirrored" system?
A:

A mirrored system involves taking your last backup and actually restoring it to another running virtual server to act as an immediately available backup server. This 2nd virtual server might be local or remote depending on the account type that you have. The advantage of a mirrored server is that you have less downtime and guaranteed system availability in the case of catastrophic failures at our data centers.

Q:
How do I get to my backups?
A:

Your backups (both local and remote) are available to you via password protected "rsync". rsync is a UNIX tool that is designed to replicate directories between systems. It is extremely powerful and effective at copying very large directory structures, both locally and remotely. With rsync you can restore any file, directory, or even an entire system from your own backups quickly and easily.

   
Administration
Q:
How do I administer my system?
A: Any way that you want to. We pre-install the "webmin" web-based admin utility. This allows you to administer your system with a web browser over encrypted connections. You can also install any other admin tool that you wish or manually edit config files with vi from a terminal login.
Q:
Can I telnet into the system?
A:

Yes, but we highly recommend that you use "SSH" (Secure SHell) instead. SSH gives you the functionality of Telnet without transmitting data in the clear. Many commercial terminal emulators include SSH support as well as a number of "free" packages as well. Visit openssh.org for more information on SSH.

Security on the Internet is important and we highly recommend that you use secure protocols like SSH, scp, https, sftp, pop3s, imaps, etc. whenever possible.