[Lustre-discuss] Number of inodes on OST

[Xiong, Jinshan]

For performance reason, the MDT creates objects on OSTs in batch with a technology called `precreate’. The MDT caches the `precreated’ objects in cache and whenever a client is creating a file on the MDT, it will allocate objects from cache. This is why you can’t see the inode count on OSTs increase immediately.

You can keep creating files from client side and monitor the inode count on the OSTs you will see the effect.

Jinshan

On Mar 10, 2014, at 7:05 PM, Chan Ching Yu Patrick <cychan at clustertech.com> wrote:

> Hi all,
> 
> I found that when I create a file, the number of inodes on OST does not increase.
> 
> Let's see the following experiment:
> 
> [root at client lustre]# lfs df -i
> UUID                      Inodes       IUsed       IFree IUse% Mounted on
> data-MDT0000_UUID         524288        3428      520860   1% /lustre[MDT:0]
> data-OST0000_UUID         393216        2398      390818   1% /lustre[OST:0]
> data-OST0001_UUID         393216        2398      390818   1% /lustre[OST:1]
> 
> filesystem summary:       524288        3428      520860   1% /lustre
> 
> 
> [root at client lustre]# dd if=/dev/zero of=/lustre/file12 bs=1M count=1000
> 1000+0 records in
> 1000+0 records out
> 1048576000 bytes (1.0 GB) copied, 46.4868 s, 22.6 MB/s
> 
> 
> [root at client lustre]# lfs df -i
> UUID                      Inodes       IUsed       IFree IUse% Mounted on
> data-MDT0000_UUID         524288        3429      520859   1% /lustre[MDT:0]
> data-OST0000_UUID         393216        2398      390818   1% /lustre[OST:0]
> data-OST0001_UUID         393216        2398      390818   1% /lustre[OST:1]
> 
> filesystem summary:       524288        3429      520859   1% /lustre
> 
> 
> You can see the number of inodes on MDT is increased by 1. But the number of inodes on OST keep unchanged.
> 
> 
> According to Lustre Manual, the inodes on OST should increase.
> 
> "Each time a file is created on a Lustre file system, it consumes one inode on the MDT and one inode for each OST object over which the file is striped. "
> 
> 
> Anyone knows why?   Thanks very much.
> 
> Regards,
> Patrick
> 
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