[Gluster-users] Concepts of Gluster: Block- vs File-based | How does cluster internally work?

Amar Tumballi amar at gluster.com
Thu Nov 25 05:59:16 UTC 2010

Hi Jens,

Read Inline..

> Some of my Questions:
> 1.) When requesting a file, is the whole file retrieved or only a portion
> of
> the file?

Gluster has 1-1 mapping between client side posix calls to server side posix
calls. ie,
when a open is called on client mount point, it will be translated to a open
on server
side (where the file actually resides). Answer for your question will be you
will get the
portion of file you requested for, and not whole file.

> 2.) Are random File accesses supported?

Yes. But, considering scenario in case of Databases, which is, random file
accesses with
query(read) for very small blocks, network delay and context switch delays
involved will
make the performance suffer.

> 3.) How does cluster internally Workd when the Database (liek MySQL) create
> a large file and then accesses this file? Does Cluster shomehow operate on
> a
> "Block Level"? How will an index-scan be translated in reagards how gluster
> will access the data on the remote system?
As I told in case of 1, Gluster will do 1-1 operation which is done @ the
mount point
over the server, hence the main issue again will be latency of the network
in all these

> I am very thankfull for any information (also links...) that help me to
> understand how gluster internally handles "file accesses" .
Lets be clear on what 'file accesses' means. I am taking it as 'read'
(considering its a
database and there will be lot of queries), but there are multiple system
calls which can
mean the same with respect to filesystem, like, access(), lookup(), stat(),


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