Compellent's replays are smarter than snapshots as they use a lot less space. DBA is used to determine where blocks were located when the replay was taken so they only increase in size when new data is written to a volume. Under normal circumstances replays will be placed on the third tier where storage costs are the lowest but you can have them on higher tiers if you wish and use data progression to migrate them down when they are unused.
As you'd expect with an enterprise storage solution, replication is a standard feature. A number of options are available as you can replicate between remote sites using either synchronous or asynchronous operations. Furthermore, it's up to you what you want to replicate as you can pick and choose from volumes and replays.
For testing we introduced the Storage Center to the lab's Gigabit network and 4Gbps FC SAN. For iSCSI testing we used quad-core Xeon 5400 Dell PowerEdge 1950 and 2900 servers running Windows Server 2003 R2 and Microsoft's iSCSI initiator. With one server logged onto a dedicated volume we saw the Iometer utility report a raw read throughput of 113MB/sec - near maximum for iSCSI over Gigabit.
With a second server logged onto the other iSCSI port we saw a cumulative throughput of 198MB/sec, showing some contention for disk resources was occurring. We tested FC performance using a Boston Supermicro dual 3GHz 5160 server equipped with an LSI Logic 4Gbps dual-port HBA. Using the same parameters as for the iSCSI test Iometer reported a good raw throughput of 350MB/sec for a single direct-attach connection.
Overall performance is good but Compellent will need to make the switch from FC to SAS drives for Tier 1 storage as they deliver equally good performance for a lot less cash and can be mixed with SATA drives in the same disk shelf. We also raised the subject of support for 2.5in SFF drives as they are more environmentally friendly and were advised this is currently on the cards as a future release.
The concept of hierarchical storage management has been around for a long time but Compellent's Storage Manager is one of few solutions currently available that is capable of managing and automating the data classification and migration processes effectively. We found it particularly easy to deploy with extremely good expansion potential and the DBA technology makes it quite unique.
Verdict
Compellent's Storage Center offers an impressive range of unique data classification features with combined support for IP and FC SANs. The controller unit hardware could be better considering the price and SAS support is currently lacking but this solution does deliver a smart data migration solution using automatically tiered storage that clearly has the ability to make big savings on network storage costs.
Series 30 Controller CPU: 3GHz Xeon 5160 Memory: 3GB FB-DIMM Storage: IDE CompactFlash card OS: eCos Linux Network: 2 x Gigabit Ethernet FC: 2-port and 4-port QLogic 4Gbps HBAs Disk array 1 - Disks: 8 x 400Gb Seagate Cheetah 10K FC drives in hot-swap carriers FC Ports: 2 x 4Gbps Disk array 2 - Disks: 8 x 500GB Seagate Barracuda ES 7.2K SATA drives in hot-swap carriers FC Ports: 2 x 4Gbps
