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Tier definition
Then it came time to identify storage tiers, requirements and features.
InfoPro determined that four tiers were needed (see "Storage tier configurations," below). The first tier would include 10,000 rpm and 15,000 rpm FC drives, with support for virtualization of other storage tiers, image copies, remote replication and LUN/volume management. The second tier would include medium-speed SAS or SATA II drives and storage, with support for various RAID levels and LUN/volume management. The third tier would include slow-speed, IP-based NAS with support for a failover NAS cluster, as well as NFS, CIFS and iSCSI protocols. The fourth tier would include disk- and tape-based backup with support for disaster recovery and vaulting. All of the tiers would need to be accessible to all of the environment's servers and applications and have built-in redundancy.
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Click here for a larger view of storage tier configurations.
At that point it was decided that a loosely coupled approach made more sense than buying an integrated system from a single vendor. With a loosely coupled system, the tiers can be upgraded individually; it's...
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also cheaper, despite opinion to the contrary, and eliminates vendor lock-in. Taking this approach allowed InfoPro to concentrate on the more critical top two tiers, leaving the NAS and backup/restore tiers for a later step in the selection process.
Product analysis
The next step was to survey the range of available midrange/enterprise-class storage products on the market. That survey produced a 30-page document detailing the options. But rather than spending a lot of energy on the wide range of products, InfoPro decided to stay with the storage marketplace's top four at the time: EMC Corp., Hewlett-Packard (HP) Co., IBM Corp. and Sun. But of those four, only storage hardware from EMC and, of course, Sun would be certified by Sun to be compatible with the agency's heavily installed base of Sun server hardware. By choosing a non-Sun-certified storage system, the agency could end up with voided warranties and be caught in the middle of vendor disputes. That certification concern became key as the project progressed.
The tier 2 products were considered first, before tier 1. Not all of the vendors' midrange storage products fit the bill for the project's tier 2 requirements. But EMC's Symmetrix DMX series products, HP's StorageWorks Enterprise Virtual Arrays (EVAs) and Sun's StorageTek 6540 arrays had excellent support for tier 2 requirements.
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