[lustre-discuss] About the data journaling mode of Lustre with ldiskfs.

[Hanggi CUI]

Hello, I'm studying the Lustre DFS in our college.

Last month, we started to benchmark the Lustre performance, between the
ordered journaling mode and the data journaling mode. We used ldiskfs as
our backend FS - which mainly based on Ext3/Ext4 (added the mount option
data=journal which ext3 defined). But we didn't get the desired results.

So I start to searching informations and analyzing the source code by
typing printk().
Then I found such things, like llite is the client VFS interface, LOD
stripe the data, osc send data to OST, fsfilt is replaced by OSD, obdfilter
named OFD which handles the read and write from OSC, etc (May not be very
accurate).
But there is no write operation functions called in ldiskfs in OST when I
write a file or running fio, so it never journal the data but only metadata.

I long for someone to tell me does lustre DFS with ldiskfs have data
journaling mode? and why?

Or I can get some more detailed documentations about this.


Thank you very much,
Hanggi.
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