Dot Hill AssuredSAN Pro 5000 review

Automated data tiering is an established technology but Dot Hill's AssuredSAN Pro 5000 takes it to the next level as it does it in real time. Other products use slow batch migration processes but Dot Hill's RealStor technology moves hot data to an SSD-based cache in seconds making it far more responsive to changes in access patterns.

In this exclusive review we put the Fibre Channel model on the lab bench. The system supplied comprised a 2U 24 SFF bay head unit with dual controllers and redundant PSUs plus a second 24 SFF bay disk shelf.

Each controller has four 8Gbits/sec FC ports and as they run in active/active mode, all eight ports are available. The controllers each have dual 6GB/sec SAS expansion ports and can handle up to eight additional expansion shelves for a total of ten.

The intuitive web interface provides an overview of all drives, tiers, pools and ports plus wizards for every conceivable task

Dot Hill's RealTier

The Pro 5000 supports up to three storage tiers with the Performance tier comprising SSDs. The Standard tier uses 10K SAS drives whilst the Archive tier employs high capacity nearline SAS drives.

Dot Hill's RealTier handles data classification and migration. It breaks the data up into 4MB pages and monitors access patterns to determine what's hot and what's not.

Using a ranking score based on page access frequency, it determines what to move up and down the tiers. RealTier scans its page scores every five seconds and moves the data to the appropriate tier.

High scoring pages get shifted to SSD whereas low scoring pages are moved to the Standard or Archive tiers. Overheads are reduced as no more than 80MB of data is moved in each five second period.

Our review system came with SSDs, 10K SAS and 7K NL SAS drives to provide three tiers for data migration

Deployment

Setup is very simple as all tier creation is fully automated. The web interface is intuitive although we had to use Google Chrome as it wouldn't display properly with IE10.

The Performance tier places the SSDs in a RAID-10 array whilst the Standard and Archive HDD tiers use RAID-6. Storage pools group the drives together and are assigned to either controller.

Our test system had four SSDs, twenty-two 10K SAS drives and twenty-two NL SAS drives. The wizard automatically created two pools each with two SSDs, ten 10K SAS plus ten NL SAS drives and kept two SAS and NL SAS drives back as global hot-spares.

For performance, you can monitor IOPS throughput for pools, tiers, volumes and controllers

Volumes and thin provisioning

The wizard then moves on to volume creation. Using Dot Hill's RealThin, thin provisioning is applied automatically and the Pro 5000 supports LUNs up to 128TB in size.

Volume creation is a cinch as you choose a name, a size and the pool you want to use. Further control over migration is possible as you can assign a tier affinity to each volume.

If the volume is likely to be used for high access data you assign it an affinity with the Performance tier. Likewise, if it's going to be used for tasks like backup data, you can assign it an Archive tier affinity.

As thinly provisioned volumes get used, alerts keep you posted on the status of physical capacity. Before it gets critical you can deploy new shelves where their drives will be added to the correct tier automatically based on their type.

The optional Data Management software bundle costs 4,000 and includes snapshots which can be run on-demand or scheduled. To rollback a volume you select this option from the Actions button and pick a snapshot to go back to. Next is AssuredCopy which copies entire volumes locally whilst AssuredRemote replicates to a remote appliance for disaster recovery.

Volumes are simple to create and snapshots can be scheduled to run at regular intervals

Performance testing

To test the Pro 5000 we used a Dell PowerEdge R515 rack server running Windows Server 2012 and equipped with a QLogic dual-port 8Gbits/sec FC HBA. Using a point-to-point link, we found the mapping process swift as the web interface automatically discovered the host on connection allowing us to assign a volume to it.

As data is placed on the volume it goes first to the Standard tier and is then moved according to access patterns. When we fired up Iometer for 64KB sequential read and write requests, it initially showed a raw throughput of around 550MB/sec.

RealTier came into play and within a minute speed has increased to 750MB/sec which equates to nearly 6Gbits/sec. We could see in the web interface that all I/O activity has shifted from the Standard to the Performance tier.

We also tested IOPS using 8KB random read and writes. Our results were better than Dot Hill's as we recorded high rates of 46,000 IOPS and 15,000 IOPS respectively. Conclusion

With a base two tier system costing around 46K and the three tier system on review costing 48K, the AssuredSAN Pro 5000 beats the competition hands down for value. Deployment is simple as most functions are fully automated, FC performance is very good and it scores highly for its real time data migration.

Verdict

Dot Hill’s real time data tiering responds faster to changing access patterns than the competition and our tests show the AssuredSAN Pro 5000 delivers top FC performance. We found it straightforward to deploy and configure. Dot Hill can’t be beaten for value either.

Chassis: 2U rack

Controllers: Dual hot-plug

Memory: 4GB cache with capacitor backup

Storage: 4 x 400GB Hitachi SSDs; 22 x 600GB Hitachi 10K SAS, 22 x 1TB Seagate 7K NL SAS

Network: 4 x 8Gbits/sec FC ports per controller

Power: 2 x hot-plug 573W PSUs

Management: Web browser, CLI