Raid 6 Storage

If two drives fail in a RAID 5 array, you lose data. RAID 6 promises more protection and better performance.

Businesses are their data. Emails, invoices, customer information, proposals, stock levels, supplier information: the list goes on and on. If that data is lost, the business is lost; at least until the data has been recovered. The statistics for businesses surviving data loss are harrowing, and those businesses are your customers. Lose data, and you’ve probably lost a customer. With the amount of data stored by even the smallest business growing exponentially, the risks of catastrophic data loss are increasing. Data needs to be stored securely and for the long term, if not for your clients’ needs, then as a result of increased business regulation.

Setting up a RAID array on a ReadyNAS Pro is straightforward. Add the drives, choose the RAID level, and let the drive do the rest.
Setting up a RAID array on a ReadyNAS Pro is straightforward. Add the drives, choose the RAID level, and let the drive do the rest.
The ReadyNAS Pro Web user interface is where you’ll create shares and set up basic permissions, as well as available protocols.
The ReadyNAS Pro Web user interface is where you’ll create shares and set up basic permissions, as well as available protocols.
You can upgrade the OS on a ReadyNAS Pro by downloading a new ROM image without leaving the Web UI.
You can upgrade the OS on a ReadyNAS Pro by downloading a new ROM image without leaving the Web UI.

You can’t prevent data loss, but you can make it unlikely. Technologies like RAID 5 increase the security of stored data, by adding enough parity information to all the disks in an array to allow recovery after a single disk failure. There’s one big problem with that; disk reliability is on a classic bathtub curve. One disk failing is likely to mean that the rest of the disks in the array are also approaching end of life (especially in an array that’s two or three years old), with a much higher chance of failing. And unfortunately, the very act of rebuilding an array can add enough stress to the remaining disks to cause one to fail during rebuilding. What was originally a way of ensuring data integrity has become another liability. Consumer and SME NAS arrays don’t have the same level of management and control as their enterprise cousins, and without effective SMART information and disk lifecycle management tools it’s near impossible to manage disks effectively.

There’s another problem with RAID 5: scalability. Once you’ve bought an array for a client you’re fixed into using the same size disk for ever. Four 250GB disks may have seemed more than enough three years ago, but now they’re almost full. If one fails, yes, you can recover it, but with disk sizes ever increasing a 250GB disk is going to cost more today than it did this time last year, as manufacturers focus on making and selling higher capacity media – it’s the same bathtub curve. A small number of NAS arrays have firmware that supports using larger disks as replacements, but you’re stuck using only part of the disk until you’ve replaced all the disks in an array with new, larger disks. It’s only then that you’re able to resize the array taking advantage of the extra capacity. The process of upgrading all the disks in an array is equivalent to rebuilding the entire array four times, with a rebuild each time you change a disk. On a full drive that can take quite some time (and can add to the risk of drive failure with aging original hardware).

Two chances to fail

If reliability is the main concern, then you should consider moving your clients to RAID 6. With RAID 6 more disk space is given over to parity information, but with a minimum array of five disks, it’s possible to recover from the failure of two disks. That’s a significant boost in reliability – and there’s still more storage than the equivalent four disk array. Plus, RAID 6 scales to larger arrays (including six disk devices).

The LaCie 5big’s status view is simple and clear. You can see what RAID level is set up, and just how much space is being used.
The LaCie 5big’s status view is simple and clear. You can see what RAID level is set up, and just how much space is being used.

Other approaches to RAID give greater storage and more flexible operations. With the proprietary X-RAID system in NETGEAR’s ReadyNAS (X-RAID 2 in the latest hardware), if you haven’t filled the array to start with, you can expand by adding additional drives and users don’t have to wait for the array to rebuild; the NAS resynchronises the array in the background. One other advantage of X-RAID is the ability to use partially matched drives. If you want to extend an array by replacing drives with large capacity units, you can, getting access to the extra capacity as soon as you’ve added at least two new drives of the same size.

The other option is a storage fabric that doesn’t need matched drives. You can get this with devices based on Windows Home Server and a new range of network-connected hardware from Drobo; these arrays intelligently place data in redundant locations on multiple disks, and at the same time support many different sizes of disk, simultaneously. If you’ve initially built a storage fabric with 500GB disks and you want to increase the amount of space, all you need to do is plug in a new disk of whatever size you want, and the array will intelligently allocate data. You’re not limited to internal bays, either, as most storage fabric devices support additional storage through eSATA and USB. eSATA is an excellent way of adding extra space, as you can now buy multi-drive bay eSATA connected storage devices, with space for several TB of extra drives that become part of the same redundant storage fabric. That’s something that a RAID array can’t give you.

Raid 6 in action

NETGEAR’s ReadyNAS Pro is a hefty piece of kit. With six drive bays there’s enough space to support most businesses’ needs, and a dual gigabit Ethernet ports increases both resilience and throughput on busy networks. If you’re using switches that support teaming, then the two ports can be given the same IP address, improving performance and allowing failover to either port in the event of a failure. If you’re running a small Windows network for a client you can make the ReadyNAS a WINS server, simplifying administration. Larger networks with Active Directories are also supported, and you can join the ReadyNAS to a Windows domain – and take advantage of its AD integration to manage users and quotas, as well as authenticating access to files and folders.

A modern network storage device needs to support more than the basic CIFS file protocol (often referred to by its old name, SMB). The ReadyNAS Pro supports NFS, for UNIX connectivity, AFP, for Mac OS, as well as Web and FTP access. There’s also Rsync support, which makes it an attractive platform for backups. For less formal occasions, there’s both iTunes and SqueezeBox streaming support as well as DLNA servers for video and picture sharing. There are also tools for secure remote connections, using a local client on PCs and laptops, rather than setting up a VPN. One useful feature is the ability to connect a flash drive and have its contents copied automatically to a directory. USB drives can also be connected for backups.

Shares are easy to add, once you’ve configured your drive. The ReadyNAS Web UI lets you add five shares at a time, and you can manage the protocols used for each share. You probably don’t want to give every share HTTP access, so you can turn it on and off as required. There’s also a built-in backup tool, which saves files onto an external USB drive or to a remote share (or another ReadyNAS). Backups can be scheduled or triggered using the front panel backup button. There’s also an online alternative, the subscription-based ReadyNAS Vault service, with 50GB of cloud storage for $199 a year.

If there are problems, the ReadyNAS will email up three email addresses. This lets you set up alerts for your clients and for you – helping you get support to them more quickly. There’s a range of different alerts, from thermal and power alerts, to disk quotas and failures. An SNMP service will link the ReadyNAS to any existing network management tools.

Our test ReadyNas Pro came with three 500GB drives. That’s plenty for a basic RAID array, but it doesn’t give you RAID6, so we installed a further three drives, taking the hardware up to its maximum six drives. It’s important to note that the ReadyNAS’s drive caddies use a non-standard screw type. You’ll need to source these from NETGEAR in advance of any hardware upgrades. Fitting the drives was easy enough, with a single button eject on the caddies. Press the button, pull the lever and you’re ready to either fit a new drive or swap out one that’s failed. Once drives are fitted to the caddies you can place them back in the server. Drives are hot swappable so they can be changed or added while the ReadyNAS is running, but it’s best to organise some downtime for major changes – if only to ensure that syncing is handled correctly. It will take time to extend the array to the new disks, and adding three new 500GB disks gave us a total storage space of 2287GB, with the whole upgrade taking under 32 hours. That’s not as bad as it seems, as each disk is added to the array in turn, and as soon as it’s ready, you can use its additional storage – plus the original storage remains available.

NETGEAR isn’t the only SMB NAS with support for RAID 6. LaCie’s 5Big is another contender. With five drive bays (and 1TB in each bay), there’s a mix of options on how to set up the drives, with RAID6 giving you nearly 4TB of storage. Again, the advantage of modern RAID techniques is that as soon as there’s capacity on the drives, it’s accessible. You’ll be able to start using the 5Big for client data while it’s still setting up and striping its array. The hardware has a striking design, looking like 2001’s HAL with a big glowing blue light on the front. Keep an eye on it – it’s your main indicator of what is happening in the 5Big (and also keep a copy of the manual to hand to decode the patterns of flashing lights).

Set up is again relatively simple, using a Web-based UI (which doesn’t work in Chrome). A desktop monitoring tool gives you basic diagnostics and connection information, as well as a link to the Web UI. Like the ReadyNAS, you’ll use it to define shares, as well as connect to Windows domains. There’s also multimedia sharing, but the range of features is nowhere near as comprehensive as NETGEAR’s. There is a built-in BitTorrent client, but unless you’re using the 5Big to download and manage Linux images it’s not really a feature we’d expect to see on a business system (and you can disable it).

RAID 6 doesn’t automatically make for a better business NAS but it does give your customers much better protection of their data. Today’s RAID devices are easier to use and more flexible, and the best examples have excellent business tools – but the HP Data Vault process that RAID certainly isn’t the only option for redundant storage.


Add-ons for RAIDiator
Download a mix of official and unofficial software for the NETGEAR ReadyNAS Pro:

The Microsoft Home Server team blog
Get the latest Home Server tips and news on Technet:

RAID Level 6
So how does RAID 6 work? A detailed description of RAID 6:

Home Server in business: HP Data Vault

Microsoft’s Home Server is a surprising business success; so much so that HP now produces a specific business edition of its MediaSmart Home Server. The X500 Data Vault looks like its consumer brethren, a small device with four internal SATA drive bays, plus external eSATA and USB connectors, but it has more storage by default, a faster CPU, a higher capacity power supply and a more robust chassis. The eSATA port is also multiplier aware, so you can daisychain an eSATA enclosure for extra capacity.

The key to using a Home Server-based system is the console, an application that connects to the device and provides a basic management interface. Use this to manage drives and storage, and to set up user accounts (there are also many add-ons from media server apps to motion-triggered video recording from surveillance cameras). Once users and machines are connected to the Data Vault, desktops and laptops will be automatically backed-up and specific file types can be transferred to a central store. It also acts as a Time Machine target, so will also support Apple networks.

Adding additional storage is easy, with hot-swappable SATA connections. The Data Vault’s drive bays are easy to remove, and new disks slot into their cradles without any screws. New drives are added to the Data Vault’s storage fabric, and you can set up folders to automatically replicate across the various drives on your server. Unlike RAID, the big advantage is that you don’t need to match drive sizes, and there’s also the option of nominating a drive as backup storage – we’d recommend an external eSATA drive but it can be internal. Plus there’s built-in remote access to the Data Vault, so employees can get at files from home or the road.

The Data Vault takes the simplicity of Home Server and tunes it to suit small business. It’s not as flexible as a standard server or a true storage array, but it’s a lot more flexible than a RAID NAS – and less than half the price of the equivalent Drobo product (which doesn’t include any drives).



Show other articles by this author

Share |
Write comment
security image
smaller | bigger



Subscribe and get the magazine in the post before it's online

Subscribe and get access to all of the back issues

To read a sample eMagazine - March 2010



If Autoruns, Processor Explorer, FileMon, RegMon and the other SysInternals tools aren't already in your arsenal, then you need to take a look at the instructions for these invaluable free utilities on the Sysinternals site. If you already know, love and tote them around on a USB stick, memorise instead; this hosts the full set of tools as EXEs files, complete with help files, so you can run them from any machine you need to work on without needing to install them or even unpack a ZIP file. read more


Unified communications


The #1 Bestseller for Only 77p