Storage Management Strategies for the CIO
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Excel Meridian Data Inc. had better success by using only Seagate Technology disk drives (Cheetah SAS and Barracuda ES SATA) in its SecurStor Astra ES, which allows users to mix SAS and SATA disk drives any way they want. Excel Meridian found Seagate's firmware does a better job handling error conditions that occur when mixing its SAS and SATA disk drives than other disk drive manufacturers' firmware.
Overland Storage's dual-controller Ultamus RAID 1200 supports disk drives from different manufacturers, but users need to follow best practices to minimize performance and interoperability problems. For instance, Overland Storage recommends users assign SATA disk drives to one controller and SAS disk drives to the other; when storage is assigned, you can look at which controller is presenting the storage to determine what the performance characteristics are on the volumes being presented.
Another best practice recommended by Overland is to install all of the SAS disk drives in the same vertical columns and all of the SATA drives in different vertical columns. Overland found that when users put SAS disk drives in rows across the array instead of columns and then create volume groups across these rows of disks, the combined rotational speed and shock of this group of SAS drives generates excessive vibration, which can affect the reliability of SATA drives in adjacent rows.
EqualLogic Inc. also supports SAS and SATA disk drives from multiple vendors within its
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PS Series storage systems, but the different class drives can't reside in the same system. However, EqualLogic's virtualization software lets you create a single storage pool that allows up to eight storage arrays (called members) to act as a single logical storage system. EqualLogic also includes performance-tuning software that load-balances hot spots across the SAS and SATA storage array members that are part of the larger storage system. This allows administrators to grant servers whatever tier of storage application owners need and then optimize the data's placement over time.
Most vendors expect to resolve most of the kinks related to mixing SAS and SATA in a single storage array by the end of this year. They anticipate that most of the current interoperability issues will resolve themselves as SAS protocols and firmware on disk drives and storage controllers matures.
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This was first published in July 2007
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