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- Approach #4: temporarily commit to another server's RAM for speed, eventually to disk
- some form of logging in RAM and batching writes to disk + checkpointing
- need to "shard" data for each server so that many servers serve as a backup for a single master to speed recovery time
- likely, backup shards will need to be able to temporarily become masters for the data while rebuilding the master
9/30 Discussion Notes
Data Durability
- New assumption: 1-2 second non-availability when failure. How long for full reconstruction?
- Issue: Estimate reconstitution of a failed node:
- No Sharding
- 64 GB per server
- 128 MB/s disk bandwidth
- No Sharding
Old Notes
Issues
- Disk write bandwidth
- Best approach to achieve good write bandwidth on disk: have at least 3 disks, one for write logging, one archiving the last amount of log data, one for compaction. Using this scheme we can completely eliminate seeks which should give us about 100 MB/s. Unfortunately, we'll need RAID as well so the total is more than 3 disks just to achieve the write bandwidth of 1 disk.
- Network bandwidth
- Incast issues on reconstruction
- Particularly at TOR switches, etc.
- Otherwise lower-bound on machine reconstruction is about 1 min.
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