Oct 032013

Learnt from the mailing list that I should not export mounting point as a brick directly, instead I should create a sub-directory under the mounting point and take it as brick, this will make life much easier later on whenever you have to do migration or re-organization (like changing replica).

Developers of GlusterFS are thinking of retiring replace-brick, from the mailing list I can see they have good point to do so (especially existing codes for replace-brick is too bad to be improved :P), however, as a (sort of) ops guy, I still prefer they can keep it since it makes ops’ life much more easier, but obviously they don’t quite agree with all requests/challenges to keep it. Anyway, it seems life will not end, it will just become a little bit troublesome, and if this is the trade-off for stability and/or performance, I’m fine with it.

Jan 132010

I have some questions about cassandra that haven’t got answer yet, I’m writing them done now to make sure I won’t forget them in the future, all these questions are pretty critical for operation:

  • How does cassandra utilize multi-core? Does it have multiple threads internally, handling different requests in different threads? If the answer is no then it will be pretty ugly since I have to run multiple cassandra instances on one machine
  • Is cassandra (maybe Java) capable to handle large memory? Make it clear, can it fully utilize 64-bit machine’s memory (8G/16G/64G)? Again if the answer is no I have to run multiple instances per machine.
  • I know cassandra can replicate data from one colo to another colo, but what I understand is that they are virtually same cluster – is it possible to make two colos both have full data set, and for client request it only return data from local node?
  • Is it possible to stream updates to cassandra to another source? What I want is capturing a live data set in another data store (such as RDBMS) for other purpose, so prefer a plug-in type of implementation so that I can grab updates and send to different downstream.

Will post more once there is anything jump into my mind, and will post answers (separated blog) if I hear of any.