[Linux-cluster] Slow Start on Storage Access

[Robert Peterson]

isplist at logicore.net wrote:
> Maybe I missed this in some of the other postings.
>
> After I mount a GFS volume, there is always a delay when I first access the 
> volume. I'm guessing somewhere between 30 seconds to 45 perhaps. This happens 
> on first access and if the node has been idle for some time.
>
> Is this because the node needs to do some calculations, get a fresh index or 
> details about the storage, then it's fine? 
>
> Mike
>   
Hi Mike,

The first access after a GFS mount will be understandably slower:  It 
can take a long
time to read in the resource group index and resource groups from disk.  
Once they're
in memory, access to them will be fast.  This should only happen after 
the mount.

It's a good question, so I added it to the FAQ.

After the system has been idle for a long time, the Linux VFS will force 
cached pages
to disk and free up the memory.  So in theory, it might take some time 
to re-read them
again.  Shouldn't be nearly as long as the first access after the mount.

Regards,

Bob Peterson
Red Hat Cluster Suite