It's so tempting to say "IDE will be OK" but how do you make the right choice?

Some Definitions:-

IDE

EIDE

ATA

(AT comes from the 1984 IBM PC/AT and stands for Advanced Technology)

ATAPI

SATA

SCSI

Only one device at a time can be active on an IDE cable bus.

It's unusual for a computer to have more than 4 x IDE buses and, because of the requirement to have a CD-ROM drive and not wanting to put 2 drives on a single cable, computers rarely have more than 4 x IDE drives.

Firewire and USB now offers more attractive alternatives for devices, such as scanners, that used to use SCSI.

Type Of Server

IDE

SCSI

disk-intensive server application such as a database

a disk-intensive server application

Mix and Match

Maybe your company needs a total of 200 gigabytes of hard disk storage but only 30 gigabytes needs to be the fast-access type for your database.

In this case it could be cheaper to have 2 x 200gbyte IDE drives in a 200gbytes RAID 1 array and 3 x 18gb SCSI drives in a 36 gigabyte RAID 5 array.

With all hard disk specifications you should consider how fast your company's data storage requirements are growing and how easy it's going to be to increase your disk drive capacity when the time comes.

What's iSCSI?

Internet Small Computer Systems Interface is an interface standard that converts normal SCSI bus traffic to a serial data stream which is then encapsulated into TCP/IP frames for sending over the Internet. iSCSI is supported by Windows Server 2003 but what possible use could it be?

Storage Area Networks are used by large organisations as a central repository of all their data which is usually only accessed by servers and is an alternative to storing it on drives directly attached to servers. Geographically separate offices can be on the same SAN and be accessing data over large distances. Super-fast Fibre Channel connections are normally used to connect servers to SAN storage devices but the maximum distance that this operates over is 120kms, iSCSI can extend the range of SANs to wherever the Internet reaches. It offers a cheaper alternative to Fibre Channel but can't operate at the same speed.

It obviously makes sense to some people to have the data you want to access stored on a hard drive 1000s of miles away.

The "I" in RAID originally stood for "Inexpensive" until the RAID Advisory Board decided that "Independent" was more appropriate.

RAID Level

Description

Advantages

Drawbacks

Read performance is improved.

The majority of the total disk space is available for data storage.

Read and write performance slows when a drive has failed.

RAID 1 mirror

(The RAID Advisory Board hasn't got around to changing this unflattering acronym.)

This is when your RAID array is earning its money so the answer should be "Nothing, as far as the users are concerned". In reality the data transfer rate of the array drops - especially with RAID 5 where missing data on the failed drive now has to be regenerated, on the fly, from the parity information.

From a network management perspective swift action is now required as another drive failure will cause total data loss (unless you have RAID 6).

The risk is now greater than if you weren't using RAID because:-

Alerts

Hot Swap Drives

It can be a real problem finding an opportunity to shutdown a busy server in order to replace a hard drive. RAID systems often allow an individual drive to be removed and replaced while the power is on - a process called hot swapping. Hot swapping uses a high quality connector system where the earth pins make contact first and break contact last as well as a RAID controller that is prepared for drives that appear and disappear without warning.

Hot Spares

A Hot Spare is a drive plugged into a RAID array that's not doing anything. It's on the "substitute's bench" ready to take over automatically if one of the active drives fails.

A Cold Spare, on the other hand, is a spare drive locked away in a cupboard somewhere.

Replacement Drive Policy

This is something that a Networking Department has and not a RAID feature.

Whether you've got hot or cold spares for your RAID array you should have worked out in advance what action you'll take when a drive fails so as to keep up the full protection offered by your RAID system. This isn't as simple as "when one drive fails we'll just buy another". Hard drives have been undergoing rapid development in the last few years leading to increased performance and capacity and so particular models often only stay current for a few months. Trying to find the same model drive as one bought 2 years ago is often impossible and RAID does function best when all the drives are the same model.

A sensible policy might be to buy 2 extra drives as cold spares when the RAID array is bought new and when the last of these has been put into service plan to replace all the drives, including cold spares, with a current hard drive model sometime soon.

I'd give Windows 2000 Server's implementation of software RAID 10 out of 10 for effort but I would never recommend anyone to use it because:-

"SCSI RAID or IDE RAID?" is the wrong question. "I need RAID, of course, but do I need SCSI or IDE drives?" is what you should be asking.

There's a discussion on this here - find out and get back to me.

NOT SCSI RAID, Serial ATA is a new enhancement of the IDE standard

That 3rd drive - the cold spare - is important  as we're going to do a nifty trick with it.

It's likely that the new drive has a higher capacity that the original so use the same partition manipulation program to expand the partition so that it occupies the whole of the SATA disk.

Backing up the whole server every day is usually too hard and so the task is split into 2:-

 It might be appropriate to do this weekly, monthly or even 6-monthly, depending on how quickly such a backup goes out-of-date.

The Mirror Crack'd

An Agatha Christie novel

So you've been successfully taking advantage of the hot-swap and auto-rebuild abilities of your RAID system to make the easiest ever complete server backups and one day disaster strikes: a rogue patch planted by a hacker on the Windows Update site is downloaded and installed on your server which then trashes the system folder making the server unable to boot and the boss is looking to you to fix it. Here's the drill:-

(Oops, better disable Windows Update first.) If that took more than 15 minutes you must have been milking it for dramatic effect.

There are still some clean-up jobs to be done.

You could now also attach the 2nd scrambled drive to another PC and make a data backup in case there's been any important new data since yesterday.

CAT5, CAT5e, CAT5e Extended, CAT6, CAT7, 350mHz cable or optical fibre?
Shielded or Unshielded?
Solid Conductor or Stranded?
Cable Box or Reel?
What about just having a wireless network instead?

When you have to choose the type of cable to install for your office network, it's a decision you don't want to get wrong.
After the cable installation phase is complete, the furniture has been put back and any damage to the decor repaired it's bad enough finding that you've forgotten a few cable runs but it's a disaster if it turns out you've used inferior cable which will have to be replaced in 18 months time.
For a typical 20 user office network you'll probably need, at most, 1200 metres of cable. Buying this amount of premium grade cable will cost you around £500. You can pick up 1200m of cheaper cable for £250 or less but this could end up costing you dearly in the long run.
The network cable you install today should be capable of handling networking standards for at least the next 10 years. Without a crystal ball, this means looking at today's leading edge technologies and taking a guess at what will be the norm a decade's time.
Gigabit Ethernet over copper, denoted as 1000base-T and sometimes 802.3ab, is already finding its way into small-to-medium-sized network installations so any cable installed today should definitely be capable of 1000mbps over every cable run.
Most traffic on a LAN consists of communication between workstations and servers which means that, with many workstations typically talking to just a few servers, the network connections to servers are the most likely places to become bottlenecks. The speed of the server link can be increased by combining 2 switch ports, 2 cable runs and 2 server network cards to double the data rate but a better way is to operate the server runs at 10x the speed of the workstation links. Today this means workstations operating at 100mbps while servers operate at 1000mbps but if we're planning for all the workstations to operate at 1000mbps how can we cable for 10gbps links to the servers? Two ways:-

Obsolete Cables

CAT5 Variants

Category 6 Networking Cable

Surely CAT7 or Optical Fibre Cabling is more Future-Proof?

Indeed they would be. CAT7 is, so far, a theoretical standard for 600mHz per copper pair and I haven't seen any for sale yet. CAT7 will require a completely different connector system - forget RJ45 - and a meticulous installation methodology will be required to achieve the high data rates. I think it will too difficult to go much beyond 200mHz per pair and will prove easier to use fibre everywhere instead.

So why not install a wholly fibre-optic network now?

Because it's will cost between 3 and 5 times as much as a CAT6 network.

However, there are sometimes good reasons to have fibre runs in your current network :-

The Other Questions

Shielded or Unshielded?

Unshielded, the cable you want is called Unshielded Twisted Pair (UTP).
Shielding means the 4 inner pairs are wrapped in metal foil before the outer plastic sheath is put on. Shielding absorbs electrical interference and so reduces its disruptive effect on the signals travelling within it. It also stops the signals in the cable itself leaking out and causing interference of their own which is useful when 2 or more network cables run alongside each other.
However the shield itself applies a capacitative load on the inner pairs which tends to attenuate high frequency signal components. Surprisingly, it's been established that, for Ethernet, unshielded cables perform better than shielded ones which is good news because unshielded cable is cheaper. You'll see Shielded Twisted Pair (STP) cable for sale because it's specified for use in other networking systems, such as Token Ring, but for Ethernet you definitely need the unshielded variety.

Solid Conductor or Stranded?

Solid.
Solid conductors have superior electrical characteristics compared to stranded but the solid copper core will break if subjected to too much movement. Stranded cable, where 6 or more thin, pliable strands of copper are woven together to form the core or the wire, can take a lot of flexing without breaking. So you should use solid conductor cable for premise wiring and stranded cable for patchcords.

Cable Box or Reel?

Reel.
A cable box is simply a cardboard box into which 300m of cable has been stuffed. You pull the cable out through a hole in one side and just keep pulling until it runs out. This is convenient but, unless you're very careful, the cable can get sharp kinks which, even though you straighten them out, subject the cable to undesirable rough handling. A reel of cable needs a dispensing mechanism to allow the reel to rotate without wandering all over the room as the cable is unwound. This can be as simple as a pole through the middle. I think that dispensing cable from a reel is the gentlest way of installing it and gives less twists than when it's pulled from a cable box.

A reel inside a box is now quite common and gets you the convenience of a box without the kinks.

Be Conscious of Fire Safety

Network cable comes with 2 types of plastic outer sheathing: the type that doesn't produce poisonous gas when burnt and the type that does. It's not mandatory to use the poisonous gas free variety in all situations but I think we should all show that we're safety conscious and pay the 30% extra that this cable costs. In the UK this cable is called LSZH (Low Smoke Zero Halogen) or another similar name and in the US is referred to as Plenum-Grade (the plenum is the space above a false ceiling).

So now at last we have the complete specification for our cable:-
We need to order a 500 metre reel of LSZH, solid conductor, CAT6 Unshielded Twisted Pair network cable - see if they have it in pink.

In the UK you can get some here.

External Grade Cable

If any cable runs will be exposed to the elements then you'll also need a smaller amount of the exterior grade version of this cable which resists the ingress of moisture and deterioration due to exposure to ultra-violet light.

Let's not bother with all this cable nonesense and have a wireless network instead.

There have been some recent improvements in wireless networking which have made it more attractive:-