Automated data tiering has traditionally only been available to enterprises with deep pockets but Dell’s new Storage SC4020 is about the change the landscape. It delivers all the storage optimization features that Dell’s high-end SC8000 appliances have to offer but at a price point that will appeal to SMBs.
The SC4020 targets businesses that don’t require the massive expansion potential offered by the SC8000 but it runs the same Storage Center (SC) software so provides identical data tiering capabilities. Put simply, it analyses data usage in real time and dynamically moves blocks to the most appropriate storage tier for the best performance.
Hot data can be moved to high performance tiers comprising SSDs and a new feature is support for write-intensive SLC SSDs in the top tier and read-intensive MLC SSDs in the second tier. The SC4020 now makes flash-based storage more affordable as businesses can use fewer SSDs to get a higher performance than a big array of 15K SAS drives.
Tasty hardware
The SC4020 is a compact 2U rack system with 24 SFF hot-swap drive bays and the choice is yours as to how you populate them. Along with SLC and MLC SSDs, Dell offers 15K SAS, 10K SAS and Nearline SAS hard disks as options.
The base price includes dual controllers each sporting 2.5GHz E3-1265L v2 Xeons and 16GB of battery protected DDR3 cache. For data ports, you can choose from controllers each with four 8Gbps Fibre Channel ports or dual 10GbE SFP+ ports and as the controllers are both active, all ports are available for use.
It may not be as big as the SC8000, but the SC4020 still offers a decent expansion potential. Both controllers have external 6Gbps SAS ports which support Dell’s SC200 and SC220 expansion shelves and you can go up to 120 drives in total.
The SC4020 automatically placed our SLC and MLC SSDs in the first and second tiers and chose the best RAID arrays for them as well
Brainy DBA
A key feature of the SC software is Dell’s Fluid Data architecture which automatically handles data migration through the various tiers. Its dynamic block architecture (DBA) provides the brains as it uses metadata tables to keep track of all blocks and stores details such as data access frequency and when it was written.
This information is used to decide which storage tier a data block should reside on and when it should be moved to a different tier. Storage is presented as virtual volumes but their actual data blocks will be located on different data tiers determined by their usage patterns.
We found deployment remarkably simple as DBA managed tier creation for us by categorizing the drives by their model, interface and, where applicable, spin speed.
Virtual Volume creation is also simplified as you can choose the best Storage Profile for each one
Our review system had six 400GB SLC and six 1.6TB MLC SSDs which were automatically placed in the first and second tiers.
We didn’t even need to worry about RAID array creation as this was all done for us. DBA chooses the array that best suits each tier and the SC4020 supports RAID0, 5, 6, 10 and Dell’s latest dual-mirrored arrays.
Easy management
We found the embedded Storage Center Manager web interface easy to use and very informative allowing us to keep a close eye on the various tiers and their performance. The SC4020 groups all physical storage into a single Disk Folder pool within which we created virtual volumes and mapped them to our test FC hosts.
Businesses with more than one SC4020 will like Dell’s free Enterprise Manager as they can access them all from a single, centralized console
Dell’s free Enterprise Manager can look after multiple arrays from a single console. It’s aimed particularly at larger businesses that are deploying SC4020 arrays to remote offices and replicating to a central SC8000 appliance.
Snapshot services come courtesy of Dell’s Instant Replays which are configured during virtual volume creation. We simply set the frequency using their scheduler and decided how many versions to keep. As we had two tiers of SSDs, Instant Replays were automatically placed on the read-intensive MLC SSDs to provide faster rollback operations.
Replication between multiple local appliances is supported and the controllers have 10GbE iSCSI ports dedicated to this function. You don’t need to reserve any data ports for failover either as Dell’s Virtual Port feature allows them all to be presented for active duty.
Unified NAS/SAN services are a possibility but only by adding Dell’s optional FS8600 appliance. With one of these linked to the SC4020 over FC or iSCSI, it can present Disk Folder volumes as network shares using its own dedicated Gigabit and 10GbE ports.
A storming performer
For performance testing, we used a pair of PowerEdge R720 servers running Windows Server 2012 R2 and fitted with QLogic dual-port 8Gbps FC adapters. Using a dual MPIO FC connection, we logged one server on to a virtual volume on the SC4020 and watched Iometer record a high raw sequential read rate for 256KB transfers of 12.2Gb/sec.
With Iometer configured with small 4KB transfer requests, it reported 160,000 and 90,000 IOPS for sequential and random read operations while for random write operations, the SC4020 delivered 34,100 IOPS. Our standard Iometer database simulation using a 66%/34% mix of random reads and writes returned an equally impressive 36,000 IOPS.
With the second server logged on also using a dual MPIO FC link, we saw high cumulative rates of 318,000 and 170,000 IOPS for sequential and random reads. Our random write test reported 60,000 IOPS while the database test running simultaneously on both servers saw a cumulative 52,000 IOPS.
- Superb performance using SLC SSDs
- Makes fast SSD arrays more affordable
- Very easy to deploy
- Automatic storage optimization
- 12Gb/sec SAS not supported
- NAS services require separate FS8600
Conclusion
The SC4020 is clearly priced to appeal to SMBs with a typical starter configuration costing $25,000 and including two 8Gbps FC controllers, twelve 1TB NL SAS drives and a full 3-year onsite 24/7 warranty. Performance using the latest SSDs is exceptional and the automated features of Dell’s Storage Center software makes deployment and ongoing storage management a piece of cake.
