3 ms·
The problem isn't necessarily speed, it's random access latency. What makes SSDs fast and "magical" is their low random-access latency compared to a spinning di
by Nextgrid 3y ago
The problem isn't necessarily speed, it's random access latency. What makes SSDs fast and "magical" is their low random-access latency compared to a spinning disk. The sequential-access read speed is merely a bonus.
Networked storage negates that significantly, absolutely killing performance for certain applications. You could have a 100Gbps network and it still won't match a direct-attached SSD in terms of latency (it can only match it in terms of sequential access throughput).
For many applications such as databases, random access is crucial, thus why nowadays' mid-range consumer hardware often outperforms hosted databases such as RDS unless they're so overprovisioned on RAM that the dataset is effectively always in there.
- baq 3y ago100Gbps direct shouldn't be too bad, but it might be difficult to get anyone to sell it to you for exclusive usage in a vm...
- Ericson2314 3y agoUm... why the hell does the network care whether I am doing random or sequential access? Your left that part out of your argument.
- Nextgrid 3y agoAh sorry, my bad. You are correct that you can fire off many random access operations in parallel and get good throughput that way. The problem is that this is not possible when the next IO request depends on the result of a previous one, like in a database where you must first read the index to know the location of the row data itself.
- Ericson2314 3y agoOK thanks yes that makes sense. Pipelining problems are real.
- Ericson2314 3y ago(The network indeed doesn't care, but bandwidth of dependent rather than independent accesses depends on latency)