{'fraction_non_alphanumeric': 0.0274822695035461, 'fraction_numerical': 0.0070921985815602835, 'mean_word_length': 5.169398907103825, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
PivotRepair: Fast Pipelined Repair for Erasure-Coded Hot Storage

Erasure coding is commonly used as a storage-efficient redundancy method for fault tolerance in cold storage. Recent studies have begun to explore the use of erasure coding in hot storage, which requires fast online recovery to preserve read performance. However, existing erasure-coded repair strategies cannot effectively handle frequent and rapidly-changing network congestions in hot storage clusters. In this paper, we present the notion of pivots, which refer to the storage nodes with sufficient available downlink and uplink bandwidths in a congested hot storage network. We propose PivotRepair, a pivot-based pipelined single-chunk repair technique that leverages pivots for enabling the fast construction of a pipelined repair tree that bypasses congested links. We further propose an adaptive scheduling strategy to improve full-node repair performance. We prototype PivotRepair and show that the repair time of a single-chunk repair and a full-node repair can be reduced by up to 71.27% and 16.50%, respectively, over state-of-the-art repair schemes.