Admission Control

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Admission control for disk-system based storage servers

• Purpose: maximum the number of subscriber requests simutanously
• service round : a sequence of k₁,k₂,...,k_n retrievals
• continuous retrieval reqirement

• additional policies
• k₁= k₂= ...= k_n
• first let k₁= k₂= ... = k_n=1, and try to increase each k

• Quality Proportional Multi-subscriber Servicing (QPMS)
• k₁=k x R¹_pl , k₂= k x R²_pl , ...
• 
• provably optimal

• dynamic admission of new requests
• problem: violate continuity requirment: different k_i^{old ,} k_i^new
• modified QPMS algorithm

Admission control in large-scale storage servers

• characteristics: VBR, tolerant for occasional errors, etc
• Purpose: admit new request according to probabilistic BW reservation, not "peak" one.
• buffer overflow:

cycle overflow:

• implementation choice: aggressive, conservative, hierarchical client classes, etc
• other considerations: disk array, chunk size, etc