Linux Consultancy Experts & Linux Solution Providers
FEATURES GLOSSARY


Address of Linux Support Company in Sheffield
Anti-Spam Services Centralized filtering of email
Bespoke Administration Tool Development Design and create a tool customised for a task a customer requires
BGP Internet Routing
We configure BGP routing for multiple upstream AS Connections
Centralised VPNs
VPNs all connect to a central server at Peerex
Compression Most tape drives offer compression, indeed tapes are generally sold in sizes such as "100MB/200MB" which really indicates a 100MB tape which can store 200MB if you get 2:1 compression. More and more data in the modern world is already compressed so you are less and less likely to see that 2:1compression. Some Disk-To-Disk storage systems include compression, and they can usually provide greater compression than tapes, but again you will see less and less savings as more data is compressed to start with. It is also worth noting that an encrypted file will rarely compress.
Database services
Postgresql or MySQL can be configured
Delivery direct to subfolders
This allows you to configure some simple rules which deliver matching messages directly into a subfolder rather than into your INBOX, saving you the effort of filing them yourself.
DHCP
DHCP is automatic network configuration service. Both the Gateway and the Small Office Server products provide this service. It allows many devices to just plug into your network and work without further configuration
Disk-To-Disk
This refers to backing up data from a disk on a server to a disk on a backup server (as opposed to a tape). This has an advantage over traditional tape based backups in that the backup can be access quickly to recover particular files. The down side is that disks are more delicate and thing such as power spikes could take out both the original server and the backup disk, this is why they are usually combined with tape backups to get the best of both worlds.
DMZ
DeMilitarised Zone . A server or servers which provide services to the public Internet. They generally need at least partial access to your internal access but are kept separate to minimise exposure of your internal network to the hostile world.
Expandable Storage
Our systems offer many options to increase storage capacity well into the future. Nearly all our systems support the basic off-line expansion, but if you expect to need more space quickly there are options such as Fast off-line expansion, reserved expansion, and hot expansion.
File storage
File storage is provided with the Small Office Server using Samba. Features include:
  • Shared folders
  • Personal folders
  • Shared printers
  • Multiple server replicated folders
  • Windows Domain authentication
Firewall
A secure-by-default firewall to help protect your network from external attack. The firewall can be configured to permit or deny services as required
Firewalls
Central firewall on server to protect server and client machines
Hot-Spare
Most RAID Controllers have the capacity to hold one or more disks as Hot-spares. This involved hold a disk in a shutdown state which is not in use but in case of a failure of another disk it can automatically be activated and joined in the RAID to replace the failed disk. This gives protection whilst replacement hardware is required as once the rebuild is completed the RAID system can suffer the loss of another drive. A single Hot-Spare can usually cover multiple RAID sets, making it a cheaper than moving from RAID 5 to RAID 6 or RAID 1 at the cost of a small window of risk between failure of the old drive and when the rebuild is complete.
Hot-Swap
This referrers to the ability to add and remove parts of a system (usually hard drives) with out having to shut the system down. All components in the chain need to support hot-swap (ie RAID controller, drive bays, and hard drive) in order for it to work. Having how-swap drive systems allows the use of Hot expansion when you run out of space.
Intranet
An internal web site on which you can provide information throughout your site or company at low cost without making it public to the outside world
iSCSI
This is SCSI over IP. It is a way of presenting disks to servers using a standard IP data network rather than a fibre channel network. It can significantly reduce costs, however IP networks a generally slower than fibre channel and are subject to interference as the network is used for other traffic as well.
Laptop-to-site VPNs
Virtually connecting your laptop to a network
Laptop-to-site
Allow roving agents access to all or part of your office resources from wherever that have access to an Internet connection.
Linux Installation
Basic installation and configuration of RHEL, CentOS, or Fedora
Local disc2disc Backup
Disaster recovery level backup to a removable disc on a regular basis
Local DNS
DNS domain for your local network. This can include automatic registration of client workstations.
Mail (POP3,IMAP,SMTP,Webmail)
Hosted centrally or on local sites
Mail
IMAP mail is provided with the Small Office Server. Features include: The service is also compatible with many external spam and virus services.
Mirroring
RAID level 1 - mirroring. This arranges the disks for maximum reliability. Better controllers give improved read performance, but write performance is usually worse. Capacity is the size of the smallest disk. Mirroring can recover (and continue) whilst at least one of the disks in the set is working correctly.
MTBF
Mean Time Between Failure . This is the average time the product lasts until it fails. Everything fails eventually, some things take longer than others. A larger MTBF is good because it means that a product is likely to survive longer. Mostly used when talking about redundant systems as they increase the overall MTBF of a system by allowing some components to fail without disabling the entire system.
NAS
Network Attached Storage - This is disk drive(s) which you can plug in to the network and access over Samba or NFS or similar network file-systems. The may or may not include fault protection and usually you are restricted to whatever file-systems they supply. Our Storage Server and Small Office Servers can act like a NAS using Samba and optionally NFS to provide access to the files.
Network Design and Specification
Analize and determine appropriate netoworking equipment and layout based on customers needs
Network Monitoring
Either monitoring from our central servers or a dedicated monitoring server onsite
NFS
Network File System . This is basically what the name says. Primarily supported by UNIX based systems.
Open Source Alternatives Consultancy
Advise of open source alternatives to proprietary products along with what the advantages and disadvantages are
Point-to-Point (P2P) Circuit
See private circuit (below) for a description
POP Collection
The server can collect from one or more POP email stores for you and deliver into the server's mail store.
Private Circuit
Private circuits - also known as point-to-point (P2P) circuits - allow disparate sites to be connected together securely via a single, dedicated data circuit. The circuits are usually provided by telecommunications companies who already have an extensive cable/fibre infrastructure, therefore allowing them to connect any two points together easily. However, P2P circuits can also connect two points together via wireless link, which obviously doesn't rely on the need for cables.
RAID
Redundant Array of Inexpensive Devices - This is the combining of multiple disks together to produce more reliable, larger and/or better performing storage. Common RAID levels are: 0, 1, 5, 6, 10. RAID levels with redundancy (data protection) can usually rebuild onto a replacement disk without needing to take the server off-line, allowing a failed disk to be recovered without effecting work.
RAID 0
RAID level 0 - striped. This arranges the disks for maximum performance and storage capacity. Unfortunately this significantly reduces the MTBF of the storage because the entire storage becomes unavailable should any one of the underlying disks fail. Capacity is the size of the smallest disk multiplied by the number of disks in the set.
RAID 1
RAID 10
RAID 1+0
This actually means RAID 1+0, although it is often used for RAID 0+1 as well. This is stacking of a RAID 1 and RAID 0 on top of each other in an attempt to get the best of both worlds. If you only have 2 or 3 drives, then this configuration usually means just RAID 1 or just RAID 0. With 4 or more drives this is a poor man's RAID 5 or RAID 6 (although there are scenarios where RAID 1+0 is the best for the job).
RAID 5
RAID level 5 - parity. This is the most common arrangement for businesses. It is a good compromise between reliability, speed, and capacity. One disks worth of storage is used to store "parity" data which allows reconstruction of the data that was on any single failed disk - ie any single disk can fail without you loosing data. Capacity is the size of the smallest disk multiplied by one less than the total number of disks. Read performance can approach that of RAID 0, however write performance can vary wildly from controller to controller with some comparable to single disk performance but others significantly slower.
RAID 6(ADG)
RAID level 6 or Advanced Data Guard. This is very similarly to RAID 5 except it uses 2 disks worth of storage for parity information and can suffer up to 2 drives failing simultaneously. Generally only available on high end RAID Controllers because the calculations for the additional parity are hard work so a faster RAID processor is required.
RAID Controller
This is a dedicated piece of hardware which manages the underlying drives in a RAID configuration, presenting the host computer with a simplified logical view. A RAID Controller usually offloads the hard work onto it's own processors, however there are versions which use the host processor and software RAID is also common as a cheaper alternative at the cost of some additional host CPU and memory usage for disk access.
Remote Configuration
We configure the machine over an internet connection
Remote disc2disc Backup
Server and workstations to systems based centrally. Costs from £15 for the first GB and £1 per GB thereafter
Remote Maintenance
We manage regular updates for the machine
Remote Working
Working from home / working on the road - Using VPN Technologies
Replication
This is the copying of data between machines in a way which preserves integrity. It may be instant or scheduled at particular times. Some forms of replication allow data to be modified at both ends, others only one end, others allow both ends but only at a certain granularity (eg a file can be edited at one end or another but not both, but another file can safely be edited at the other end).
Router Configuration
Configuration of network routers including dynamic routing (OSPF/iBGP/eBGP/RIP)
Samba
Samba is an open source implementation of the network file-system used and provided by Microsoft Windows (SMB). The name Samba is also often used to mean the Windows version and both are interoperable. Many other operating systems such as Mac OS X and Linux can access files on Samba Share
Samba Share
This is a particular directory on the host file-system which is made available via Samba.
SAN
Storage Area Network - Basically a raid controller for many machines. SANs generally allow you to join together a group of disks in a redundant/fault-safe manor to gain large amounts of storage which are then divided out to multiple servers. This generally means that you need less disks overall as you can assign to each server only what it requires. Disks can also be shared between servers for those file-systems which support it. This is all about offering redundant storage devices to the host machines which can then put their own file-systems on them. Our Storage Server can act like a SAN, using iSCSI to deliver logical disks to target hosts.
Security Audit/Analysis
Analysis of firewalls, running services and permissions. Advice on security improvements
Server Hosting
Hosts servers centrally in a secure environment
Shared Mail
Allows multiple people from within the company to access one or more common mailboxes. Useful for incoming group emails.
Single Instance Storage
This is the combining of files in a backup such that if 2 (or more) servers have a copy of the same file it is only stored once to save on the space. Savings in order of 30% are quite possible using this technique, although saving vary a lot from site to site. Unfortunately tapes get much less benefit from Single Instance Storage as they don't have random access.
Site-to-site VPNs
Connecting sites together over the internet
Site-to-site
Connectivity between two permanent remote locations. Allows more expensive resources to be consolidated on one site and accessed from all locations.
SMTP Delivery
The server supports mail delivery via the industry standard SMTP protocol
Subfolders
In Mail subfolders allow you to sort your email by creating and moving files into other folders than your INBOX. For example, you might create a folder called "Amazon" where you place all emails from Amazon so that you can easily find them. See also: delivery direct to subfolders
Thin Clients
Lightweight clients for connecting to a central server. Available in multiple configurations
VPN
Virtual Private Network - Connect your sites to each other transparently (site-to-site) to allow access to common services and/or connect your mobile clients into your network (laptop-to-site) to give agents on the road full access to all the resources they might need
WAN Advice (ADSL/X.21/LES)
Analysis and advice on what type of WAN Circuit is most appropriate for the customer
WebMail
Access to Mail via a web interface. Useful to get at your email when you are at someone else's machine or working remotely with a web browser.
Web Hosting
Centrally hosted websites
Web Proxy Servers
Manage web access restrictions, caching and logging
Windows to Linux Migration
Smooth convertion from Windows to Linux servers
X.21
X.21 is the protocol used by leased lines. Our integrated X.21 support allows you to skip an expensive leased line router as our Firewall/Gateway server can connect directly to the line.

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