Automated Storage Tiering - Sub-LUN tiering

Excellent comparisons between Automated Storage Tiering technologies of different vendors.

• http://searchstorage.techtarget.com/feature/Sub-LUN-tiering-Five-key-questions-to-consider
• http://www.computerweekly.com/feature/Automated-storage-tiering-product-comparison
• http://searchsolidstatestorage.techtarget.com/news/1378753/Vendors-take-different-approaches-to-automated-tiered-storage-software-for-solid-state-drives
• http://www.emc.com/collateral/software/white-papers/h8058-fast-vp-unified-storage-wp.pdf

I personally believe automated storage tiering (AST) is really important for dynamic virtualized datacenter and because AST differs among vendors I'm going to collect important information for design considerations.  I don't want to preferred or offend against any product. Each product has some advantages and disadvantages and we as infrastructure architects has to fully and deeply understand technology to be able prepare good design which is the most important factor for reliable and well performed infrastructure.

Good mid-range storage products on the market (my personal opinion):

• DELL Compellent
• Hitachi HUS
• EMC VNX

DELL Compellent
Tiers: SSD, SAS, NL-SAS (SATA)
AST Sub-LUN tiering block: 512kb, 2MB (default), 4MB
Tiering optimisation analysis period: [TBD]
Tiering optimisation relocation period: [TBD]
Tiering algorithm: [TBD]
QoS per LUN: no

Hitachi HUS (HUS 110, HUS 130, HUS 150)
Tiers: SSD, SAS, NL-SAS (SATA)
AST Sub-LUN tiering block: 32MB
Tiering optimisation analysis period: 30 minutes
Tiering optimisation relocation period: [TBD]
Tiering algorithm: [TBD]
QoS per LUN: no

EMC VNX 
Tiers: SSD, SAS, NL-SAS (SATA)
AST Sub-LUN tiering block: 1GB
Tiering optimisation analysis period: 60 minutes
Tiering optimisation relocation period: user defined
Tiering algorithm:

During user-defined relocation window, 1GB slice ae promoted according to both the rank ordering performed in the analysis stage and a tiering policy set by the user. During relocation, FAST VP relocates higher-priority slices to higher tiers; slices are relocated to lower tiers only if the space they occupy is required for a higher-priority slice. This way, FAST VP fully utilized the highest-performing spindles first. Lower-tier spindles are utilized as capacity demand grows. Relocation can be initiated manually or by a user configurable, automated scheduler. The relocation process targets to create 10% free capacity in the highest tiers in the pool. Free capacity in these tiers is used for new slice allocations of high priority LUNs between relocations.

QoS per LUN: yes


I've collected information from several public resources so if there is some wrong information please let me know directly or via comments.