Over the past year I have been experimenting and using NAS appliances with solid state drives. As most of you know, NAS appliances have typically been used to store and manage large amounts of data such as photos, videos etc. With the latest Qnap x70 lineup, SSD caching has come to the SMB and even home user if you so decide to purchase. That being said, most NAS vendors are going away from the typical RAID setup in their appliances opting for a more refined and flexible storage pooling or tiered storage if you would like to call it. Storage pools offer a tremendous amount of flexibility, as you can expand volumes without rebuilding an entire array. For instance, about a month ago I decided my TS-470 could benefit from an extra 4TB drive where previously I had an SSD in for caching. All I had to do was turn off SSD caching, shutdown the NAS and swap drives. Loading back up the Web GUI in QTS and telling the NAS to add the new 4TB volume to my existing array.
Similarly, you could also setup two independent volumes, one with SSDs and the other a capacity driven HDD volume. You may ask what gain is there in using solid state drives over hard drives in a NAS application, after all the NAS is limited to its Ethernet connection. To explore this, I have put together a few benchmarks, with IOMeter to explore the performance differences between HDD and SSD in a typical NAS appliance. The NAS I am using is the Netgear RN104, a Marvell based appliance aimed at entry-level users.
Accurately testing any type of NAS appliance requires matching pairs of drives, as such I have put together four Seagate 4TB NAS HDDs and four 200GB Seagate 600 Pro Enterprise SSDs. The system running the test is a GIGABYTE Z77 with 16GB of memory an i5-3570K and a dual port Intel NIC of which I have teamed or aggregated the connections using The 802.3ad LACP protocol. The connection is made to the Netgear RN104 using iSCSI Multipath with both integrated NICs aggregated under the 802.3ad protocol.
One thing to note is everyday data that you push back and forth on your NAS appliance is written and read to the drives sequentially. However, for those that run applications from the NAS or use the iSCSI protocol you can take advantage of the NAS performance more effectively by mounting LUNs to your PC as if it were direct attached storage. Using this protocol over SMB shares allows you to take advantage of the SCSI command set and performance therein.
As I stated above, those that routinely run applications from their NAS appliance will see the most benefit with random data. One such use case could be running Outlook 2013 on multiple PCs with one PST file located on the NAS. Above you can see the SSD excels with random data across the entire QD range, though typical users wont get into the higher tiers your looking at QD1 to QD8 for normal use.
Random write shows the same story, the SSD excels as it does when connected to your system.
Moving on we have sequential read results where you can see again the SSD excels here as well.
Sequential write is the only place we find the HDD and SSD remotely close to each other, what we would call the peak performance of the appliance itself.
The largest performance gain you will get from SSDs is with latency and yes we can achieve that snappy feeling with NAS appliances too.
If you have ever tried to copy or move data to and from your NAS appliance, and had to wait before the transfer would start that would be latency, or waiting for the platters to spin up if you use standby. Again you can see how well the SSD does and predictably so.
As the price per GB of SSDs has dropped over the last year no longer are we using 30 and 60GB drives for our OSes, we have moved on to higher capacity 256GB,512GB and for some 1TB drives, so why are we still using HDDs in NAS appliances? The only answer I could come up with is simple, capacity. With the latest lineup of appliances from both Netgear and Qnap we have a higher level of data storage, giving us the ability to utilize storage pools instead of the traditional RAID array. With solutions like these you can setup a highly available SSD array for data you access the most or more often and a HDD array consisting of a high capacity platter drives, giving you the best of both worlds, Of course then we have to wrestle with data redundancy and there will be some trade-offs going from a pure platter based solution to a mix of SSD and HDD. For instance in a four bay appliance you could use three platter drives and one SSD, giving you the option for RAID5 redundancy on one volume and SSD latency one the other. Additionally you can setup a backup schedule on the NAS and have it replicate your SSD data to your array on a daily or weekly basis.
Being the Consumer Storage and Networking Editor here at TweakTown does allow me to look at and test a lot of the latest products coming to market and one thing I've always enjoyed was trying new things, like putting SSDs in NAS appliances and giving it a go. At any rate, we find out what works and what doesn't if there are performance gains or not and in the end help consumers with their purchase decisions. If you have any ideas you want me to try with storage or networking devices, or have an idea for future testing please don't hesitate, you can find me quite easily in the forums or drop me a line in email. Until next time. TB