What are drives and servers and how do I use them?
Drives are like physical hard disks or CDs. They store your operating system, applications and data, and are persistent across server reboots.
Servers are virtual machine instances, and may have one or more drives attached to them. They are either running or powered off. When a server is running, the cloud provides VNC access. When a server is powered off, you can configure the CPU, memory, drives and IP addresses it is in use.
Some of our competitors have less-flexible products in which every server has exactly one drive. Our approach is more general, allowing you to attach several drives to a single server, or build several alternative configurations which boot from the same drive. (However, only one running server can access a given drive at any one time.)
How are the sizes of drives and servers measured?
Similar to a physical hard drive, drives are measured in gigabytes (GB). Servers have two adjustable sizes: the amount of memory (in MB) and the amount of CPU bandwidth (in core-MHz).
How large a server and drive do I need?
This will depend entirely on what you plan to use your server for: everybody’s requirements vary. However, a good starting point is to configure with the same sizes as you would use if you were purchasing a physical server for your application.
How do I create a server?
* On the right hand side of the control panel in your account, you can follow the Add Server wizard to create a server. We offer various options:
o Use a pre-installed system.
o Self-install from a CD. There are many installation CDs to choose from, for different OSes( Operating System).
o Upload your own CD and boot your server from that.
Make sure you create a sufficiently large drive to store your operating system, applications and data.
How do I access and control my server?
The cloud provides basic VNC access to servers, which works from the BIOS onwards, and allows you to install, configure and recover your operating system, even if nothing is running inside your server. In normal use, you should access your server by a native method (e.g. SSH, VNC installed inside your operating system on port 5901, Windows Remote Desktop/RDP), which will provide superior performance.
What VNC software do you recommend?
Our VNC service requires a reasonably recent client. TightVNC works well on Windows, and clients based on gtk-vnc such as Vinagre work well on Linux. The RealVNC Enterprise Edition Viewer is good on Linux, Windows and MacOS if you select “Always use best available colour quality”. The Linux and MacOS versions of this are available as a free download under ‘Enterprise Edition Viewer’ on the RealVNC web site.
Neither the Apple Remote Desktop VNC client, Chicken of the VNC, nor JollysFastVNC works correctly on MacOS as they do not support some of the newer protocol features which we use.
What is the maximum size of a single server or drive?
The largest single server you can create is 32000 core-MHz CPU, 12288 MB RAM, with one or more 2TB disk drives.
What is the minimum size of a single server or drive?
The smallest single server you can create is 500 core-MHz CPU, 256 MB RAM, with a 1 GB disk drive. This is typically sufficient for a Linux appliance such as a DNS server.
How many servers and drives can I have?
There is no limit to the number of servers and drives that you can have in your account.
What physical infrastructure is SKALIcloud based on?
The virtualisation hosts in our Serdang IDC have dual eight-core AMD Opteron 6128 at 2.0GHz with 48GB of RAM and 3x 2TB drives each per node. They run our in-house cloud hosting platform, which is built on open source technologies including Linux, qemu-kvm, LVM and iSCSI. The disks are arranged into RAID 1 pairs, and virtual disks are allocated out of this pool of RAID 1 arrays.
How are my servers and drives distributed between physical hosts?
When you create a drive, it is allocated on a randomly chosen host with sufficient free space.
When you start a server, our system prefers to place it on the same physical host as its drive(s). If this is possible, the server can directly access the underlying physical disk. Otherwise, if the host containing the drive is already too busy, the server will be started on a nearby host and it will access its storage by peer-to-peer iSCSI over gigabit Ethernet.
One of my drives is a backup of another. Can I specify that the two drives should be allocated on different physical hosts for better resilience?
Yes, although this is a new feature and only possible through the API at present. When you create the second drive, pass in ‘avoid DRIVE1′ where DRIVE1 is the UUID of the first drive.
What do you mean by core-MHz?
The effective speed of modern CPUs is determined both by the clock speed of the processor (in MHz) and the number of independent execution units (cores). For a given processor design, the available CPU bandwidth is roughly proportional to the product of these two elements.
Substantively, if you create a virtual server with 2000 core-MHz of CPU allocated, you should expect performance roughly equivalent to a single core of AMD Opteron 6128 clocked at 2.0GHz, and this performance varies linearly in proportion to the core-MHz number.
How do I set the number of CPU cores?
This is under the advanced settings on the server configuration page. (Click Edit when your server is powered off to find this page.)
What is the maximum CPU for a single server?
The maximum CPU value for a single server is 32000 core-MHz.
What is the minimum CPU for a single server?
The minimum CPU value for a single server is 500 core-MHz.
What do the Shutdown, Hard Power Off and Hard Reset buttons do?
The shutdown button sends an ACPI power button signal to the server operating system, exactly as the ‘soft power-off’ button does when pressed on a physical machine. Normally operating systems are configured to shutdown or hibernate when this is done.
The hard reset button sends a non-maskable interruption to the server CPU in exactly the same way the reset button does on a physical machine. You should only use this if your server has crashed; otherwise you should reboot from inside your operating system.
The hard power off button behaves exactly as if you have switched off a physical machine by turning off the power. You should also only use this if your server has crashed; otherwise you should shutdown using the button or from inside your operating system.
What is the maximum memory for a single server?
The maximum memory value for a single server is 12288 MB RAM. Our physical node has up to 48GB, however we have reserved the extra resources for your bursting capacity.
What is the minimum memory for a single server?
The minimum memory value for a single server is 256 MB RAM.
What happens to my data when my server shuts down?
Data stored on your virtual drives is persistent and will be available when you restart your server, just as it would be on a physical hard disk. This means that you can install software and save data exactly as you would on a physical server, unlike some other cloud solutions.
What is the maximum size of a single drive?
The maximum size for a single drive is 2 TB on RAID 1.
What is the minimum size of a single drive?
The minimum size for a single drive is 1 GB on RAID 1.
How do I attach more than one drive to a server?
You can set this in the server configuration page. (Click Edit when your server is powered off to find this page.)
Can I attach one drive to more than one server?
No. However, you can run file sharing protocols such as NFS or Windows File Sharing from one server to another over a private network VLAN.
I have uploaded an ISO9660 image (.iso file). How do I boot a server from it?
On the server configuration page, set the drive media type for the drive containing the image to CD-ROM and ensure the boot radio button is activated next to it. If you are installing a server from the CD, remember you will also need another drive attached onto which to install your operating system.
What is the difference between IDE, SCSI and Virtio drives? Which do you recommend?
In practice you should stick with the IDE emulation, which offers good performance and compatibility. The SCSI and Virtio drive types are intended for specialised applications. (Note that our Virtio drives possess writeback caching enabled, thus you will need Linux 2.6.32 or later, which supports barriers over Virtio, to be able to use these safely. No released version of the Windows virtio drivers support barriers, so the Virtio block transport cannot yet be used safely under Windows.)
What storage performance can I expect?
You should be able to achieve around 30-40MB/s streaming read and write performance from your virtual drives. However, contention with other users accessing the same underlying RAID arrays can result in lower performance, especially at peak times. This affects writes more than reads as we cannot safely cache disk writes as aggressively.
How do I get a static IP address?
Servers are configured with a dynamic IP by default, but you can purchase a subscription for as many static IP addresses as you need through the subscriptions page in your account. You then need to allocate the actual addresses by clicking ‘add static IP’ on the control panel, and configure the static IP in your server configuration.
How do I use multiple static IPs on the same server?
You will need to configure this inside your server. The networking option on the server configuration page sets the IP address only in which the server is supplied by DHCP (Dynamic Host Configuration Protocol) and which is used for VNC (Virtual Network Computing). This should be the ‘primary’ IP of the server, but you can also use any other static IPs in your account if you configure these inside your server operating system.
How do I remove a static IP address from my account?
Since all the static IP addresses in your account are available to be used by all servers at any time, then you will need to stop your servers before you will be able to delete a static IP address from your account.
How do I set reverse DNS for my static IP addresses?
Please email us with the IP address, host name and account email details and we will set this up for you.
What internet bandwidth can I expect? Is this limited?
In each of our availability zones, your virtual machines are connected directly to a major ISP backbone network at 100Mbps or 1Gbps speed. We do not cap or throttle the connection.
How can I track my bandwidth usage?
A report of received, transmitted and total bandwidth for your account is shown on your billing page, with links to display traffic graphs. You can edit the URL parameters on these graphs to adjust the timeframe and offset.
Per-server traffic graphs are available from the control panel. There is a link next to the VNC IP address when the server is running.
What happens if I exceed my subscribed bandwidth limit?
In the event that you have exceeded your subscribed bandwidth limit, you will be charged the hourly burst rate for additional bandwidth usage and this will be deducted automatically from your prepaid balance. When your prepaid balance runs out there is a buffer of 10-20 GB which you can use. After that your servers will be automatically shut down.
As your prepaid balance is being used up, you will receive warning emails, letting you know you should top up (or increase your subscriptions).
Do you charge for network bandwidth?
Yes. We charge for both inbound and outbound traffic. We do not cap or throttle the bandwidth to / from your servers. See our pricing page for details – View More
Will I be charged for bandwidth between my servers?
Yes, we charge for all bandwidth usage that does not go over a private VLAN.
What is a private VLAN and why would I use it?
A VLAN acts like a private Gigabit Ethernet Switch connecting your servers together via a second virtual Ethernet card in each server. This network is isolated from the internet and other customers. Bandwidth over a VLAN is not chargeable.
How can I configure a private VLAN?
First, purchase a private VLAN subscription. Then add it to your account in the control panel. Then, edit each server’s configuration in order for you to be able to use your private VLAN. This is under the Advanced settings.
Do private VLANs work between your availability zones?
No. A private VLAN can only be set up within a single availability zone, so any traffic sent between our different availability zones will be charged at the standard rates.
What is the difference between the virtual network cards you offer? Which do you recommend?
We recommend the Intel PRO/1000 as it is the fastest, and is widely supported in modern operating systems. If you are running a relatively old OS, such as Windows XP, the Realtek RTL8139 is an older model which should be supported by your OS.
Do you block any network traffic?
We block outbound connections to smtp, ftp, ssh and telnet servers to prevent abuse of our trials for sending spam or conducting dictionary attacks against other internet hosts. Port 5900 is used for running the VNC console.
How can I send email from my servers? Can you lift the SMTP block?
# We are happy to lift the SMTP( (Simple Mail Transfer Protocol) block to enable you to s send emails from your servers. Please email us to request this, confirming that:
* any mailing lists you run on the servers are strictly opt-in, and
* all messages sent to those mailing lists contain instructions on how to unsubscribe.
How can I connect to my server over a VPN?
You would need to run VPN (Virtual Private Network) software inside your server, just as if it were a physical server.
How can I upload my own ISO CD images?
# You are welcome to provide your own ISO CD images to use on your servers. You can upload these in one of three ways:
* by using our API (Application Programming Interface) with the skalicloud-upload script;
* by FTP (File Transfer Protocol) to ftp.skalicloud.com with username ‘elastic’ and password ‘elastic’; or
* if the drive is less than 1GB, use the drive upload web form found under ‘Edit drive’.
How can I upload my own server images?
You can use any of the methods mentioned in the previous question to upload a server image to your account. Using our API upload tool is likely to be the best choice if the image is large, as this uploads in chunks and has the option of resuming an interrupted upload.
We can also accept USB hard drives with drive images on, to copy across directly. Please contact us if you would like further details of this.
What format server images do you support?
We accept only raw drive images that are the same as a physical drive, with block device, partition tables etc.
How can I migrate Linux KVM or QEMU virtual machines into your cloud?
If your drive is already in the raw format supported by these hypervisors, it is then ready to be uploaded using our API upload tool unchanged, as described above.
If your drive is in qcow2 (QEMU Copy On Write), format, you will need to convert it to raw format before uploading. You can do this with the command:
qemu-img -f qcow2 -O raw drive.qcow2 drive.raw
where drive.qcow2 is the qcow2 file you need to convert to the raw file drive.raw.
How can I migrate VMware virtual servers into your cloud?
You will need to convert the drives in VMware vmdk format (Virtual Machine Disk format) into raw files before you can upload them with our API upload tool. To do this, you will need the qemu-img command distributed as part of qemu and qemu-kvm. Run it as:
qemu -f vmdk -O raw drive.vmdk drive.raw
to convert the vmdk drive drive.vmdk into a raw file drive.raw.
How can I migrate physical servers into your cloud?
If you have physical servers that you would like to migrate into our cloud, you should boot your server from a live CD and then run the skalicloud-upload script to upload the hard disk block device. However, please note that uploading a large drive this way can take a very long time depending on your internet connectivity. It may be quicker to install afresh in our cloud and copy your data across.
Can I send you data on a physical disk to copy into my account?
Yes, please refer to the posting above.
How do I resize my server?
When your server is powered off, go into the server configuration page, then simply adjust the CPU and memory settings.
Can I change the size of my server whilst it is running?
No. Operating systems are not able to recognise changes of this sort and would crash if we enabled them.
How do I grow my disk?
To increase the size of your drive, shut down the server that it is attached to, choose ‘Edit’ for that drive in your control panel and increase the size in the dialog. After resizing the disk, you can now restart your server attached to it; but will then need to grow any partitions and filesystems on it to utilise the extra space. (Our preinstalled linux images do not have partitions but just a single filesystem filling the entire drive, so it is sufficient to run resize2fs directly on the hard disk block device node to grow this filesystem.)
How do I shrink my disk safely?
It is very important to shrink the size of your filesystem and any partitions by using your operating system BEFORE you attempt to shrink the drive itself! If you fail to do this, it will result in the end of the filesystem to be chopped off when you shrink the drive which will lead to serious corruption. If in doubt, we strongly advise against any attempts at shrinking a drive due to this risk. However, once you are sure that it is safe to do so, you can shrink the virtual drive by shutting down the attached server and decreasing the drive size via the control panel.
How do I scale automatically with load?
You can use our API to start and stop servers when your application detects that it needs extra computing power. Building an application which scales across multiple machines like this is done in the same way as it would be on a physical hardware which you could programmatically turn on and off, but is beyond the scope of this FAQ.
How do you recommend configuring server clusters appropriate for each stage in my website’s growth?
* Whilst the exact answer will vary according to your web application’s architecture, we recommend the following cluster architectures to back a typical site as it grows, progressing in order:
1. Single small server with standard disk, running entire LAMP stack.
2. Single large server with dedicated disk, running entire LAMP stack.
3. Multiple large servers in classic 3-tier web application architecture, interconnected over private network VLAN:
ß Clustered database servers with dedicated disk
ß Front-end application servers with standard disk
ß Load balancer(s) running Pound, HAproxy (High Availability Proxy)
Note that in the second stage a single larger server with dedicated disk will characteristically give better performance than splitting immediately into multiple small servers, since disk I/O is improved and there are no extra latencies from cross-network communication.
What can I do with your API?
Our API allows you to do everything you can do on our web control panel: the web control panel is actually implemented on top of the API.
How do I use your API?
Please refer to our API page for details of how to use our API.
How do I start a powered off server using your API?
Powered-off servers exist only at the web interface level and are not yet exposed through our API. If you create a running server through the API, it will disappear when powered off. Persistent servers will be exposed in the next API release, which is due very shortly.
What redundancy does your infrastructure provide?
Our virtual drives are allocated on RAID1 disk arrays. These provide a similar level of reliability to RAID1 on a traditional dedicated server, and ensures that any failure on one virtualisation host will not affect others. By contrast, many of our competitors use centralised disk servers (SAN/NAS) which act as a single point of failure.
What is your uptime guarantee?
Our SLA offers compensation whenever we fail to meet our 100% uptime guarantee. Please refer to our Terms of Service for more details
What solutions do you recommend for backups?
We do not provide an integrated backup service, but you can backup your data yourself, either by running a backup server on our infrastructure or by using a third-party backup service such as rsync.net.
If you run your backup server in the same availability zone as the main server, you can transfer data between the two for free over a VLAN, but both would be affected by a catastrophic failure of the entire availability zone. On the other hand, you can survive such failures if you provision your backup server in another availability zone, however the bandwidth utilised between the two sites will be billable.
Can I make a backup copy of a drive?
We provide a drive copy function which duplicates a drive. You have to power down a server while this takes place, and it may take some time if the drive is large. We aim to introduce instant snapshots in the medium term run, which will be possible even while a server is running.
How do I set up a firewall on my servers?
We recommend running a firewall software inside your servers (Windows built-in, or Linux iptables).
How can I disable VNC on a server?
On the server configuration page, you can disable VNC (Virtual Network Computing) access by leaving the VNC password field blank.
How can I encrypt VNC connections to a server?
We do support TLS VNC through the utilisation of the VeNCrypt extensions, which some VNC clients support. You can enable this option through the advanced settings in the server configuration page. Note that there are several incompatible schemes for TLS on VNC. It is noted that gtk-vnc/vinagre on Linux is a popular client that works with VeNCrypt
What access do SKALIcloud staff have to my servers?
SKALIcloud staff do not have access to your server passwords. The only access they have is the ability to see the VNC display, which they may use from time to time to check that your server is running.
How do I set up load balancing between my servers? Which tools do you recommend?
We recommend that you set up a small server in your cluster, running a load balancer, such as HAProxy or Pound, and connect it to your backend web servers over a VLAN.
How can I configure my system to fail over between your two clusters?
The easiest way of configuring failover is to use a DNS-based failover method. Set a low TTL on the A record for your website to avoid excessively long caching, and alter this to point to the backup server when the production server is down. There are third-party DNS providers who offer this kind of service as part of their DNS hosting offering.