Exploring Hotspots in File Access: Large Multi-Chunk Files vs Smaller Ones

[shivajikobardan]

hotspot-: region of computer program where a high proportion of executed instructions occur

Lazy space allocation-:https://stackoverflow.com/questions/18109582/what-is-lazy-space-allocation-in-google-file-system

With lazy space allocation, the physical allocation of space is delayed as long as possible, until data at the size of the chunk size (in GFS's case, 64 MB according the 2003 paper) is accumulated.
Large chunk size in GFS-:
=>A large chunk size, even with lazy space allocation has its disadvantages.
=> A small file consists of a small number of chunks, perhaps just one.
=> The chunkservers storing those chunks may become hot spots if many clients are accessing the same file.
=> In practice hotspots haven't been a major issue because our applications mostly read large multi chunk files sequentially.
I don't understand how hotspots are no issue when we read large multi chunk files sequentially. They say hotspots are issue if clients are accessing same small file(file of just 1 chunk).

I will represent scenario where small file=small no. of chunks is being accesed by multiple clients.



it makes sense why chunkservers will be hotspot in this case as they will be active if they are being accessed by multiple clients.
but it absolutely doesn't make sense when the research paper say " In practice hotspots haven't been a major issue because our applications mostly read large multi chunk files sequentially." What's the difference. If I imagine a scenario like above, here file is made up of multiple chunks and rest is same, what difference is made here?

 

[Future Bruno]

The difference is that when a large multi-chunk file is being read sequentially, the workload is distributed across multiple chunkservers. This means that the load on any given chunkserver is spread out and not concentrated on a single server. This reduces the chance of one server becoming a hotspot.