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Sun, 12 Aug 2007

More on DRBD.

I've just read its Linux Euroconf paper. DRBD is not RADI1 at all, it is a single storage, which mirrors all write requests to remote node. So until resync is completed, you are not allowed to read (and write) to given blocks, you have to reconnect to slave node when master one is dead, two-nodes-only setup (commercial version has a support for a bit more easy three-node setup).

Contrary distributed storage allows to form a device on top of any number of remote and local nodes, reading is performed from the 'nearest' node (in terms of the current head position), writing is always mirrored to all nodes and if one of them has failed, reconnection will happen automatically. Resynchronization (in testing stage, not yet 100% ready) happens when system reconnects to remote node. Resync infomation is not stored on devices itsefl, which allows to mount them independently, but also means that after one node is dead and not yet completely recovered and main node crashes, nodes will contain different data and it is up to administrator to decide which one is ready. In future versions I can add possibility to save sync bitmap on the storage itself (this can be simple, but this removes possibility to mount remote node's data as standalone system).
If main node has failed, the array is destroyed and one needs either to form new one on the different node or just connect to another node, but if main node has crashed, application is dead too...

So, DRBD does not look similar to DST, this is a different project with own aims and results.

/devel/dst :: Link / Comments (0)

Die Hard.

All four films were produced by John McTiernan.
John McFuckingClane.

/other :: Link / Comments (0)

Compilers.

This thread about using volatile (which I consider as a bad hack) in atomic operations forces me to think about why the hell there is only one compler in the opensource (and actually the rest too) world?
Thinking...
Not that I'm going to start writing new compiler tomorrow, I basically do not have enough knowledge (likely, but I did not even try) now, but I'm thinking, why not to fill this gap.
There is number of projects (start from security systems, the simplest case is OpenBSD) which do want a compiler, which would allow to easily add own security frameworks, and to have a competitor for benevolent dictator in compiler land. I think the compiler, which can compile Linux kernel, is a good development milestone.

/devel/other :: Link / Comments (4)

Mercury rising.

Just watched a film - very interesting, why the main bad guy, NSA colonel btw, has russian (or slavic) surname Kudrov...
Day of old films - of course all "Die Hard"s.

/life :: Link / Comments (0)

Blues and jazz pubs in Moscow.

I'm looking for small place with live blues and/or jazz music in Moscow.
If you know interesting one, please drop a line in comments.

/life :: Link / Comments (2)

Let it be a day of the rest.

I got bottle of red Chile merlot wine "Canto de flora" and decided to devote the whole day to lazyness - I did not do this quite for a while already (I do not even recall when I spent the whole day not doing something), and now I feel myself good.
Have a nice day.

/life :: Link / Comments (2)

NFS directory reading speed.

Here is a graph of ls -l of the NFS exported and directly (ext3).
Gap is huge.



I tried different NFS export flags (sync/async), mounting it with and witout locks - result is essentially the same.

/devel/other :: Link / Comments (6)