Multiple DataFileDirectorie and disk failure

[ma...@gmail.com]

HI，folks:

 

It’s seems cassandra can use multiple DataFileDirectory:

…..

  <DataFileDirectories>

      <DataFileDirectory>C:\Data1</DataFileDirectory>

      <DataFileDirectory>C:\Data2</DataFileDirectory>

      <DataFileDirectory>C:\Data3</DataFileDirectory>

         ……

  </DataFileDirectories>

…..

 

>From code I found cassandra will create a directory for each table (keyspace), now I have a node which have 12 disk, and I plan to mount each disk

onto each directory:

 

C:\Data1\key_space1

C:\Data1\key_space2

C:\Data1\key_space3

C:\Data2\key_space1

C:\Data2\key_space2

C:\Data2\key_space3

C:\Data3\key_space1

C:\Data3\key_space2

C:\Data3\key_space3

 

the questions are:

1.       How does SStables of one key-space distribute among multiple data directory?(what distribute policy?)

2.       What fault-tolerant policy does cassandra utilize to against disk failure?

3.       If one disk down, What impact does one key-space have on reading and writing?(does whole key-space become unavailable?)

 

Thanks very much!!

---------END----------

 

Re: Multiple DataFileDirectorie and disk failure

[Jonathan Ellis <jb...@gmail.com>]

On Mon, Dec 21, 2009 at 2:37 AM,  <ma...@gmail.com> wrote:
> 1.       How does SStables of one key-space distribute among multiple data
> directory?(what distribute policy?)

round-robin

> 2.       What fault-tolerant policy does cassandra utilize to against disk
> failure?

node-level replication

> 3.       If one disk down, What impact does one key-space have on reading
> and writing?(does whole key-space become unavailable?)

no, but you should run nodeprobe repair to re-replicate the data from
the dead disk to good ones.

-Jonathan