Hi, Gavin gao A very interesting new feature. Our team once discussed implementing the ssd cache layer in bookkeeper, because our other internal message queues, such as kafka, use this architecture. We hope that bookkeeper storage can be applied to the same machine type, but because Other internal work, this work has not been formally arranged in daily work.
Adding the ssd cache layer, I believe that the read and write timeout caused by the hot traffic of the local HDD disk will be effectively improved. I'm really looking forward to this feature. :) Thanks, wenbingshen Gavin gao <gaozhang...@gmail.com> 于2023年5月26日周五 10:37写道： > In a typical bookkeeper deployment, SSD disks are used to store Journal log > data, while HDD disks are used to store Ledger data. Data writes are > initially stored in memory and then asynchronously flushed to the HDD disk > in the background. However, due to memory limitations, the amount of data > that can be cached is restricted. Consequently, requests for historical > data ultimately rely on the HDD disk, which becomes a bottleneck for the > entire Bookkeeper cluster. Moreover, during data recovery processes > following node failures, a substantial amount of historical data needs to > be read from the HDD disk, leading to the disk's I/O utilization reaching > maximum capacity and resulting in significant read request delays or > failures. > > To address these challenges, a new architecture is proposed: the > introduction of a disk cache between the memory cache and the HDD disk, > utilizing an SSD disk as an intermediary medium to significantly extend > data caching duration. The data flow is as follows: journal -> write cache > -> SSD cache -> HDD disk. The SSD disk cache functions as a regular > LedgerStorage layer and is compatible with all existing LedgerStorage > implementations. The following outlines the process: > > 1. Data eviction from the disk cache to the Ledger data disk occurs on a > per-log file basis. > 2. A new configuration parameter, diskCacheRetentionTime, is added to > set the duration for which hot data is retained. Files with write > timestamps older than the retention time will be evicted to the Ledger > data > disk. > 3. A new configuration parameter, diskCacheThreshold, is added. If the > disk cache utilization exceeds the threshold, the eviction process is > accelerated. Data is evicted to the Ledger data disk based on the order > of > file writes until the disk space recovers above the threshold. > 4. A new thread, ColdStorageArchiveThread, is introduced to periodically > evict data from the disk cache to the Ledger data disk. >
