Posted in Technology, tagged big data, different, performance, scale on 30 August 2013| Leave a Comment »
A lot of people seem to think performance is about doing the same thing, just doing it faster. That’s not what performance is all about. If you can do something really fast really well, people start using it differently.
Linus Torvalds (speaking about git)
Because more is not just more. More is different.
Posted in PhD, Technology, tagged cache, disk, memory, numbers, performance, reference on 11 June 2010| Leave a Comment »
I was watching Jeff Dean’s keynote presentation for the ACM Symposium on Cloud Computing 2010 (SOCC) that was held yesterday and I found this very interesting bit of information. This is so useful that every Computer Scientist and Engineer should learn it by heart!
| Operation | Time (nsec) |
| L1 cache reference | 0.5 |
| Branch mispredict | 5 |
| L2 cache reference | 7 |
| Mutex lock/unlock | 25 |
| Main memory reference | 100 |
| Compress 1KB bytes with Zippy | 3,000 |
| Send 2K bytes over 1 Gbps network | 20,000 |
| Read 1MB sequentially from memory | 250,000 |
| Roundtrip within same datacenter | 500,000 |
| Disk seek | 10,000,000 |
| Read 1MB sequentially from disk | 20,000,000 |
| Send packet CA -> Netherlands -> CA | 150,000,000 |
These numbers give you some insight into why random reads from a disk are a really bad idea.
This piece information complements the very nice image from Adam Jacobs, and his excellent “The Pathologies of Big Data” article.
Random is BAD (and SSD is NOT going to solve the problem)
What should we learn from all this stuff?
Kenkyuu 