On 01/19/2017 12:34 AM, Song Liu wrote:

Media health monitoring is very important for large scale distributed storage systems. 
Traditionally, enterprise storage controllers maintain event logs for attached storage
devices. However, these controller managed logs do not scale well for large scale 
distributed systems. 

While designing a more flexible and scalable event logging systems, we think it is better
to build the log in block layer. Block level event logging covers all major storage media
(SCSI, SATA, NVMe), and thus minimizes redundant work for different protocols. 

In this LSF/MM, we would like to discuss the following topics with the community:
    1. Mechanism for drivers report events (or errors) to block layer. 
       Basically, we will need a traceable function for the drivers to report errors 
       (most likely right before calling end_request or bio_endio).  
  
    2. What mechanism (ftrace, BPF, etc.) is mostly preferred for the event logging?

    3. How should we categorize different events?
       Currently, there are existing code that translates ATA error (ata_to_sense_error) 
       and NVMe error (nvme_trans_status_code) to SCSI sense code. So we can 
       leverage SCSI Key Code Qualifier for event categorizations. 

    4. Detailed discussions on data structure for event logging. 

We will be able to show a prototype implementation during LSF/MM. 

Very good topic; I'm very much in favour of it.

That ties in rather nicely with my multipath redesign, where I've added
a notifier chain for block events.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
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