NAS Options for Shared Storage in the Cloud - Page 3


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NAS Options

Network attached storage (NAS) is probably the most pervasive shared storage technology and has been around for a fairly long time. The NFS bits, both the server and the client, are included with virtually every single Linux distribution. Plus, Windows XP and Windows 7 have the ability to be NFS clients for no additional cost (things change with Windows 8). However, there are commercial products that provide NFS capability for Windows as well.

Using the compute, network, and storage options in AWS with the NFS software bits, there is a large range of possible NAS/CIS shared solutions. Let's start with the "do-it-yourself" option before moving on to pre-packaged NAS solutions.

Do it yourself

As I previously mentioned, virtually every distribution of Linux comes with the capability of NFS, both client and server. You can spin up a Linux instance in Amazon, configure the storage, be it ephemeral or EBS or both, however you like, and then configure the NFS server (i.e. /etc/exports), and export the storage. Conceptually, this is a fairly easy way to get shared storage, and it works. However, the devil is in the details (as always).

I won't go over the details of creating a NAS in this article, but you can look around the web for some tutorials about taking disks in your system and exporting them to clients via NFS and CIFS (using Samba). In the case of Amazon AWS the "disks" are EBS Volumes and/or ephemeral storage. There is a good video from AWS re:Invent 2013 about NFS and CIFS Options for AWS. In the video, some of the details of creating a NAS solution are covered along with some recommendations and general rules of thumb. There are also some pointers to software that can help you get started.

Pre-packaged NAS solutions

With the rise of technical computing in the public clouds there has been a corresponding increase in the number of pre-packaged NAS solutions. These are AMIs that can be used to quickly create NAS solutions using Amazon instances and/or EBS volumes. These commercial offerings have an hourly pricing associated with them on top of the hourly pricing for the instances and the EBS volumes. Each of them has their own unique features and capabilities.

In this section, I'm going to cover a NAS AMI that is available in the Amazon Marketplace. It is representative of what is possible for pre-packaged NAS storage solutions in the cloud.

SoftNAS: SoftNAS has created a NAS gateway, called the SoftNAS Cloud, that utilizes AWS instances, as well as Amazon EBS and S3 storage, to create a NAS in the cloud. It uses ZFS as the underlying file system, giving you SSD caching (presumably using the SSD ephemeral storage in the compute instance), compression, deduplication, scheduled snapshots and read/write clones. The company states that they can achieve up to 10,000 IOPS using EBS and S3 storage, or 40,000 IOPS when using SSD caching. The standard SoftNAS Cloud product scales to 20 TB but the SoftNAS Professional Edition can scale to 154TB of space. (It appears they have tested it up to 500 TB.)

The SoftNAS Cloud can utilize EBS or S3 storage to create something of a tiered storage. It appears that you can combine EBS storage and what the company calls "S3 Cloud Disk" into a RAID-1 mirror configuration. This gives you the potential of improving performance while taking advantage of the redundancy of S3. The nice thing about the S3 Cloud Disk is that it is like "thin provisioning" because you can "allocate" some storage capacity to it but you actually don't pay for it until you use it.

The SoftNAS Cloud provides NFS, CIFS and iSCSI access to servers. Note that using Amazon's VPC, you can connect local servers to the AWS instances so that the both the local servers and AWS instances can connect to the same storage with varying degrees of performance, but still sharing the same storage.

One nice feature is that the SoftNAS team has created a nice GUI front end to the SoftNAS Cloud product. It allows you to manage and configure the storage, and it also includes some basic monitoring data that you typically see in NAS (i.e. write and read throughput, etc.). You can configure deduplication and compression via the GUI but be aware that you need to pay attention to the instance you are using for the NAS gateway. In general, compression requires more CPU power, and deduplication requires more memory.

You can also create a second SoftNAS Cloud instance and do replication between them (basically asynchronous replication). SoftNAS calls this Sanreplicate, and it is useful if you need to ensure that your data is accessible. (Note: I don't know the technology they are using but it appears to be rsync.) If you need synchronous replication then you could use something like DRDB to replicate between SoftNAS instances when writing data. However, you should think about doing this before using the NAS gateway; otherwise, you will have to unmount the exported file system from the clients, synchronize the two instances and then re-export the file system.

If you want to get started with SoftNAS, there is a Marketplace AMI (Amazon Machine Image) that you can use. Prices vary depending upon the instance you are using. For example, the t1.micro instance is $0.02/hr (pretty cheap for learning about SoftNAS). The prices go up to $2.40/hr for a c2.8xlarge instance (32 vCPUs, 60 GB memory, 10GigE). For the SoftNAS Cloud prices you pay, you get support from SoftNAS. Alos, you can use one instance of SoftNAS for 30 days for no software charges (you still pay for the AWS instance and EBS volumes).

One feature you should definitely keep in mind is that EBS volumes have snapshot capability. This means that you can take a snapshot of the EBS volumes used by SoftNAS and then either use these to create a replica of the original data.

While SoftNAS is relatively easy to get started, you should definitely stop and think about what you need from a Cloud NAS storage solution. What kind of performance do you think you need? How much capacity? Do you need to replicate the NAS instance or is there another mechanism for keeping a copy of your data somewhere? What is the network configuration you want to use? Do you need the provisioned IOPS capability of EBS or not? What kind of network do you need? Do you need to increase the capacity at some point?

Sit down and carefully plan what you need before you start building something—it can save you time, money and some frustration.

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