In Google File System,hotspots haven't been a major issue because our applications mostly read large

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.

https://imgur.com/a/B2F4VLh

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?

 

I am not quite an expert to discuss this type of questions, but I found something that might be helpful

one answer:
Jitesh Nambiar, Student at SUNY Buffalo. Interested in Information Retrieval.

XFS makes use of lazy evaluation techniques for file allocation. When a file is written to the buffer cache, rather than allocating extents for the data, XFS simply reserves the appropriate number of file system blocks for the data held in memory. The actual block allocation occurs only when the data is finally flushed to disk. This improves the chance that the file will be written in a contiguous group of blocks, reducing fragmentation problems and increasing performance. Reference : http://en.wikipedia.org/wiki/XFS#Delayed_allocation

Allocate-on-Flush: http://en.wikipedia.org/wiki/Delayed_allocation

this also might be helpful links too:

https://www.develop-bugs.com/article/20269819/What+is+lazy+space+allocation+in+Google+File+system

https://csharp.developreference.com...Net+SaxonApi+throwing+out+of+memory+exception

 

thanks man

 

mamm