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ScyllaDB: Drop-in replacement for Cassandra that claims to be 10x faster

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Re: ScyllaDB: Drop-in replacement for Cassandra that claims to be 10x faster

#41

Post by acconsta »

lastofus wrote: post #38
jandrewrogers wrote: post #24

Earlier quoted context omitted.

Over the last decade, the distributed system nature of modern server hardware internals has become painfully evident in how software architectures scale on a single machine. The traditional approaches -- multithreading, locking, lock-free structures, etc -- are all forms of coordination and agreement in a distributed system, with the attendant scalability problems if not used very carefully. At some point several yea…

How does one bypass the kernel for network and disk IO? I've never heard of doing this before (e.g. IO is always a system call)

Basically mapping the device registers into user space and doing exactly what the kernel would do, but without the syscall overhead.

Some researchers made a big splash at OSDI by doing this securely:

http://people.inf.ethz.ch/troscoe/pubs/peter-arrakis-osdi14....

Re: ScyllaDB: Drop-in replacement for Cassandra that claims to be 10x faster

#42

Post by ogrisel »

est wrote: post #28
jandrewrogers wrote: post #24

Earlier quoted context omitted.

Over the last decade, the distributed system nature of modern server hardware internals has become painfully evident in how software architectures scale on a single machine. The traditional approaches -- multithreading, locking, lock-free structures, etc -- are all forms of coordination and agreement in a distributed system, with the attendant scalability problems if not used very carefully. At some point several yea…

I really appreciate your insight, but I didn't understand why you keep implying "open source" as some kind of lack-behind design?

I agree. I suppose that the vast majority of closed source DBs do not follow this shared nothing architecture either.

Re: ScyllaDB: Drop-in replacement for Cassandra that claims to be 10x faster

#43

Post by acconsta »

dorlaor wrote: post #40
mappu wrote: post #16

Numbers look great, but so do /dev/null's. What guarantees does it make? Has it been through Jepsen yet?

It's planned. However, I don't believe we'll pass it today. We're targeting GA for Jan and we'll give it our best shot.

Yeah, I was wondering about that. It looks like you guys have done some brilliant work with the storage engine, but reimplementing all the distributed logic is another (possibly bigger) project.

Re: ScyllaDB: Drop-in replacement for Cassandra that claims to be 10x faster

#44

Post by sargun »

cbsmith wrote: post #27
acconsta wrote: post #17

Earlier quoted context omitted.

Honestly, Cassandra's Jepsen didn't set a high bar: https://aphyr.com/posts/294-call-me-maybe-cassandra/

Except that problem has been largely addressed now.

How so? The fundamental flaw was using timestamps.

Re: ScyllaDB: Drop-in replacement for Cassandra that claims to be 10x faster

#45

Post by jandrewrogers »

est wrote: post #28
jandrewrogers wrote: post #24

Earlier quoted context omitted.

Over the last decade, the distributed system nature of modern server hardware internals has become painfully evident in how software architectures scale on a single machine. The traditional approaches -- multithreading, locking, lock-free structures, etc -- are all forms of coordination and agreement in a distributed system, with the attendant scalability problems if not used very carefully. At some point several yea…

I really appreciate your insight, but I didn't understand why you keep implying "open source" as some kind of lack-behind design?

In practice, open source databases use more traditional, simpler architectures for which there is a lot of literature. Ironically, you see a lot more creativity and experimentation in closed source database architectures, and this has accrued some substantial benefits to those implementations.

The architecture at the link looks unusual compared to open source databases but it is actually a common architecture pattern in closed source databases with significant benefits, particularly when it comes to performance. There is a lot of what I would call "guild knowledge" in advanced database engine design, much like with HPC, things the small number of experts all seem to know but no one ever writes down.

It is a path dependency problem. Most open source databases were someone's first serious attempt at designing a database, a project that turned into a product. This is an excellent way to learn but it would be unrealistic to expect a thoroughly expert design for a piece of software of such complexity on the first (or second, or third) go at it. The atypical quality of PostgreSQL is a testament to the importance of having an experienced designer involved in the architecture.

Re: ScyllaDB: Drop-in replacement for Cassandra that claims to be 10x faster

#46

Post by _Codemonkeyism »

cbsmith wrote: post #26
_Codemonkeyism wrote: post #25

Earlier quoted context omitted.

10x speedup (same algorithms, same architecture) replacing Java with C++ is not possible (~2x at max). One of the latest benchmarks I've seen is "Comparison of Programming Languages in Economics" [1] for code without any IO just number crunching, has a 1.91 to 2.69 speedup of using C++ compared to Java. So any code involving IO is going to be slower. Replacing bad Java code with excellent machine aligned C++ a 10x sp…

It's particularly flawed given: a) IO is such a large portion of the problem b) Hypertable isn't just way, way faster.

"a) IO is such a large portion of the problem"

I'm very interested in a cluster benchmark therefor, say 10 servers, as Cassandra claims to scale very well. With a cluster IO has a higher performance impact than one server with local RAID IO.

Re: ScyllaDB: Drop-in replacement for Cassandra that claims to be 10x faster

#47

Post by _Codemonkeyism »

_Codemonkeyism wrote: post #25
dschiptsov wrote: post #10

Finally, back to sanity of great old-school products, like Informix, by dropping Java (the whole scam) for C++14 and by paying attention to details of an underlying OS (again). Same trend, by the way, is in Android development.

10x speedup (same algorithms, same architecture) replacing Java with C++ is not possible (~2x at max). One of the latest benchmarks I've seen is "Comparison of Programming Languages in Economics" [1] for code without any IO just number crunching, has a 1.91 to 2.69 speedup of using C++ compared to Java. So any code involving IO is going to be slower. Replacing bad Java code with excellent machine aligned C++ a 10x sp…

[Edit: The LMAX guys showed how much more performance is possible with aligning code with CPU/hardware (in this case for Java)

http://mechanical-sympathy.blogspot.de/ ]

Re: ScyllaDB: Drop-in replacement for Cassandra that claims to be 10x faster

#48

Post by technion »

lastofus wrote: post #38
jandrewrogers wrote: post #24

Earlier quoted context omitted.

Over the last decade, the distributed system nature of modern server hardware internals has become painfully evident in how software architectures scale on a single machine. The traditional approaches -- multithreading, locking, lock-free structures, etc -- are all forms of coordination and agreement in a distributed system, with the attendant scalability problems if not used very carefully. At some point several yea…

How does one bypass the kernel for network and disk IO? I've never heard of doing this before (e.g. IO is always a system call)

Oracle has long argued the value of bypassing the file system and associated kernel drivers with its raw devices and ASM. It'd be interesting to see such a thing land in other platforms.

Re: ScyllaDB: Drop-in replacement for Cassandra that claims to be 10x faster

#49

Post by glommer »

_Codemonkeyism wrote: post #25
dschiptsov wrote: post #10

Finally, back to sanity of great old-school products, like Informix, by dropping Java (the whole scam) for C++14 and by paying attention to details of an underlying OS (again). Same trend, by the way, is in Android development.

10x speedup (same algorithms, same architecture) replacing Java with C++ is not possible (~2x at max). One of the latest benchmarks I've seen is "Comparison of Programming Languages in Economics" [1] for code without any IO just number crunching, has a 1.91 to 2.69 speedup of using C++ compared to Java. So any code involving IO is going to be slower. Replacing bad Java code with excellent machine aligned C++ a 10x sp…

It doesn't come from the choice of language. It comes from the choice of architecture. C++ is a tiny piece of the puzzle. It would have been hell to implement such an architecture in Java bit this is as far as the language matters.

Re: ScyllaDB: Drop-in replacement for Cassandra that claims to be 10x faster

#50

Post by glommer »

cbsmith wrote: post #26
_Codemonkeyism wrote: post #25

Earlier quoted context omitted.

10x speedup (same algorithms, same architecture) replacing Java with C++ is not possible (~2x at max). One of the latest benchmarks I've seen is "Comparison of Programming Languages in Economics" [1] for code without any IO just number crunching, has a 1.91 to 2.69 speedup of using C++ compared to Java. So any code involving IO is going to be slower. Replacing bad Java code with excellent machine aligned C++ a 10x sp…

It's particularly flawed given: a) IO is such a large portion of the problem b) Hypertable isn't just way, way faster.

IO is not only a large part. It is the main part. That is why it is important to get it right : scylla for instance does not leave the cache to the OS. It has its own caches for everything. Never blocks on IO or page faults because all IO bypasses the kernel. And those are just two tiny examples.
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