BeyondRAID Technology
Storage without limitations.
RAID (Redundant Array of Independent Disks) technology was first introduced as a concept in the late 1980s. It was designed to provide larger logical storage containers that were capable of protecting data from a random disk drive failure. Since then, a majority of businesses and many individual professionals have leveraged RAID-enabled products to storage large amounts of valuable data.
Drobo was founded to create storage that breaks down many of the inherent barriers of deploying traditional RAID. The result was a new and innovative technology called BeyondRAID that delivers all of the benefits of traditional RAID—providing greater capabilities and drastically simplifying implementation and management—and as a result, leaving the limitations behind. This next-generation of storage virtualisation technology brings together enhanced protection, reliability, expandability, and ease-of-use.
Challenges of Traditional RAID
To deploy traditional RAID-enabled storage, you first had to learn about RAID and understand the necessary prerequisites before the storage can be consumed by a computer and its applications. This raises the question: should all individual professionals and IT administrators have to learn what an enterprise storage administrator knows to deploy RAID-level storage? And to the observation that there must be an easier way to deploy storage!
First, you need to decide up front how many disks should be in a RAID group. Do you need 2, 3, 4, or even more disks? What capacity disks should you purchase? This is a critical decision because with most arrays, you can't grow the RAID group with additional disks after it's already in use. It's challenging to predict how much storage space you'll need two years, one year, or even six months from now. So if you plan to deploy traditional RAID, it's smart to invest in a lot of storage initially so you can grow into it over time. You just have to accept the added capital cost.
When the RAID group is full, you must create a new RAID group to store more data. This is because many arrays do not offer functionality to grow a RAID group. And if you're out of empty drive bays, then this new RAID group needs to be on a different storage array. If you don't want to manage your data on different RAID groups, you'll need to set up a new array that has more capacity, migrate the data from the old array to the new array, and then figure out how to repurpose the old array. It's easy to see how this could be time consuming and costly.
Often, you must determine the RAID protection level when you deploy, because many arrays don't allow you to change RAID levels. Even when they do, the entire RAID set must be rebuilt. This can sometimes take days and even weeks depending on the size and number of drives in the RAID group. When changing RAID levels, the volumes, or LUNs, may not even be available for use. Can you handle that downtime?
When a drive fails in a traditional RAID array, the RAID group is in a degraded state in which the data is not protected. Some arrays even prevent writes when they're in a degraded state. The array will be this way until the failed drive is replaced with a new one. Hot spare functionality was created to automate this, but what are hot spares but unused storage that just consumes a drive bay and waits for a failure?
If you are not familiar with RAID arrays, you may be thinking, "Wait a minute … you're telling me that I have to burn multiple drives for RAID protection and then I need a hot spare to sit there in case a primary drive fails? How much usable storage will I actually have?" That's a good question.
In this 12-drive array, each of three RAID groups has their own parity drive plus a hot
spare in case of a drive failure. 4 of the 12 drives are not used to store data.
On top of all of that, in most RAID arrays, you cannot use different sized drives in a RAID set. This means that if you want to leverage larger drives, you either need to create a new RAID group containing that larger drive or you need to migrate your data from the old RAID group to a new RAID group and then repurpose the old drives.
Rather than pulling from a common pool of free space, RAID groups are
carved up into volumes (LUNs) and assigned to servers.
Once you get past the challenges of RAID groups, you have to carve up the available storage by creating volumes, or LUNs, and assign those volumes to a specific server. It's like renting storage space in a self-storage facility—space is assigned to you and whether or not you use it, it cannot be assigned to anyone else. A single computer or server owns the entire capacity of that volume. That's a lot of free space tied up by individual computers—yet another challenge that makes storage provisioning difficult.
Moving BeyondRAID
Drobo's BeyondRAID technology solves these fundamental issues with traditional RAID while delivering much more. Built on an advanced virtualisation platform, BeyondRAID chooses the correct protection algorithm based on data availability needs at any given moment. Since the technology works at the block level, it can write blocks of data that alternate between data protection approaches.
Drobos, based on BeyondRAID, interact with computing systems in the same manner as storage arrays using traditional RAID, so installing a Drobo allows you to maintain your current operating system and file system. This eliminates the challenges and costs when moving to a new storage technology.
Now let's see how these challenges are addressed with innovative Drobo BeyondRAID technology.
BeyondRAID technology built into every Drobo addresses these shortcomings and makes virtualising disk drives usable by everyone. BeyondRAID provides these enhancements over traditional RAID:
Thin Provisioning and Reclamation:
One of the toughest challenges of storage management is to decide how much storage space is needed for a computer or application. If you allocate too little you may run out of space, too much and you waste valuable storage resources by tying it up to one computer.
Thin Provisioning is a fundamental capability of BeyondRAID, allowing you to allocate the right amount of storage for today, while allowing you to expand capacity by just adding a drive to the Drobo or replacing an existing drive with a larger one.
With Drobo, this expansion is nearly instant and occurs when a new or larger drive is inserted without any disruption in service. If you are running low on space, all you need is another hard drive to add to the Drobo. Adding more drives instantly increases usable storage capacity.
Adding additional drives instantly increases usable storage capacity, in this case, from
1.5 TB to 2.5 TB (assuming single disk redundancy).
While 4- and 5-bay Drobos often contain one thinly provisioned 16 TB volume, 8- and 12-bay models allow for user-controlled volume creation. These volumes (or LUNs) are called Smart Volumes™ and they pull needed storage from a common pool (thin provisioning) and then return deleted blocks back to the common pool (thin reclamation), preventing free space from being tied up by any particular server.
As volumes consume storage, they pull from a common pool of free space and when
storage is freed up, it is relinquished back to the same pool.
Space allocation is automatically managed, which helps maximise storage resources. You can try this out for yourself. If you have a large file on a volume and then you delete it, you will see the free space of the Drobo grow, making that freed up space available to any other volume. Even enterprise-class arrays with thin provisioning do not return consumed storage back to a common pool at this granular of a level.
Mixed Drive Utilisation:
With Drobo you can insert any drive of any size and it will be used. With traditional RAID (RAID 5, for example), all drives must be the same size to be utilised. What if you have a set of three drives in a RAID group and you want to expand? With traditional RAID, you must migrate data off your drives, add a new drive that is the same size as the others, reformat the RAID group, and then migrate the data back onto the drives. Not only does this take a lot of management time, it incurs potential downtime; you need available storage space in another array to temporarily store the data. With Drobo, if you're running low on space and you have an empty drive bay, just add another drive. Even when your Drobo is full, just remove the smallest drive and replace it with a larger one.
If mixed drive sizes are used in traditional storage, drives of the same size must be in their own RAID group, drastically reducing storage utilisation and flexibility. Drobo utilises mixed drive sizes in a single group.
To best learn how mixed drive utilisation works in a Drobo, play with our interactive Capacity Calculators. They allow you to simulate putting drives of mixed sizes in a Drobo to see exactly how the drives will be used.
Automatic Protection Levels:
A Drobo always sets itself up to protect from random drive failure. Unlike traditional arrays, there are no options in a Drobo to turn off drive protection (nor would you want to). In a Drobo, the only options are Single Disk Redundancy and Dual Disk Redundancy. You can switch between these protection levels on the fly and Drobo adjusts the data on the drives appropriately.
BeyondRAID only has two protection levels:
- Single Disk Redundancy provides protection from a single drive failure at a given time (similar to RAID 5). Storage capacity is maximised with this option.
- Dual Disk Redundancy provides protection from two simultaneous drive failures (similar to RAID 6). You invest by consuming an additional drive but gain the added protection. Even when the Drobo is automatically rebuilding from a previous drive failure, you are protected from another drive failure, ensuring that your data remains available and accessible.
Drobo guarantees that the best algorithm is used to protect from drive failure depending on the number of drives that are inserted without any user configuration or intervention. There is no need to learn about RAID levels or how mirroring or striping works. For example, if you enable Dual Disk Redundancy and have only two drives inserted, Drobo will operate, but will tell you to insert another drive to operate in a fully protected state.
About RAID Levels
With a Drobo, you do not need to learn about all the various RAID levels for drive protection/performance/capacity trade offs, but it doesn't hurt to know a little:
RAID 0 – drives are "striped" together and provides no data redundancy to protect from a drive failure. While performance often increases with RAID 0, reliability decreases each time a drive is added to the set.
RAID 1 – drives are "mirrored" together and provide data redundancy between two or more drives. Most often two drives exist in a mirror and performance is similar to that of a single drive.
RAID 5 – drives are "striped" together like with RAID 0, except parity data is created and spread across all drives in the set to prevent from a single drive failure. This RAID level is common because it scales while keeping the cost of drive redundancy down.
RAID 6 – drives are "striped", with parity data spread across all drives similar to RAID 5, but in this case, the parity data is stored twice. This protects against two drive failures. Often, RAID 6 has decreased write performance compared to RAID 5 because of the added time to calculate and store an additional set of parity blocks.
There are other RAID levels such as RAID 4, RAID 0+1, and RAID 50—all of which makes determining the proper RAID level even more complex.
Virtual Hot Spare:
A Drobo utilises all drives all the time with no drives sitting idle waiting for one to fail. With some traditional RAID systems, a drive can be marked as a "hot spare," waiting on standby for a drive failure so it can take over. That's just an unused drive that you have to pay for taking up a valuable drive bay.
With a Drobo, no wasted hot spare is needed for automatic rebuild in the event of a drive failure.
If a drive fails in a Drobo and there is enough free space available, Drobo will automatically move data around to return to a protected state. No user interaction is required. This is called a "virtual hot spare" because the unused space in a Drobo IS the hot spare.
Once the Drobo automatically recovers from a drive failure by using the free space available, if sufficient amount of free space is still available, the virtual hot spare will still be there. With traditional storage, the admin would have to replace the failed drives and elect a new hot spare.
Data Aware:
Drobos are data aware, that is, they intelligently handle data for added resiliency, performance, and management. This is different than just storing data at logical block addresses like RAID. Being data aware informs the capacity gauge on the front of the Drobo, quickly recovering in the event of a drive failure, enabling intelligent tiering of data, and much more.
Data is analyzed in-flight as it enters a Drobo and is intelligently placed on the drives.
As data is written to the Drobo, it is analyzed in flight and intelligently placed on the media to maximise protection and performance.
Drobos are also aware of the data placement inside the file system. So Drobo can display an accurate capacity gauge without even being connected to a computer or to enable Smart Volumes as described earlier in this chapter.
It is trivial to allocate clusters on demand when data is being written to a Drobo, but storage arrays are not naturally aware of when data is deleted from a file system. In a thin provisioned system such as Drobo, this is important information to prevent leaking clusters, or losing free space to a specific volume over time.
Instead of free space being tied up a volume, a Drobo is data aware: free space is pulled
from a common pool and returned to that pool when the file system deletes data.
Drobo understands and monitors what goes on in the file system to track when logical block address (LBA) ranges are freed up. It can then de-allocate the associated clusters and return them to the global pool of free space. This technology allows the Drobo to be very efficient and free space is not tied up by any specific volume or the assigned server.
Drive Re-ordering:
With traditional RAID groups, drives have to be in a specific order. With disk packs in a Drobo, ordering does not matter. This allows Drobo disk packs to be moved to another Drobo and even reordered, while still functioning. Try that with RAID and see what happens to your data!
Unlike traditional storage, drives in a Drobo do not have any specific number or order, so they can
be placed in any slots and function normally. It's one less thing to worry about.
Drive Handling
As mentioned in the previous section, drives are not tied to a specific bay or order. Using drivespecific information, a unique identifier is assigned to each drive. Because drives in a Drobo are identified by their unique identifier, they can be placed in any slot position, and reordered, while still being recognised as the same logical drive.
Drives in a Drobo are logical in nature because they have a unique identifier,
allowing them to be placed in any bay and function normally.