counters for misaligned (partial?) writes

[evilensky]

Greetings,

What are the best-practice counters for monitoring misaligned, partial writes, specifically due to misaligned VMware virtual machines?  The best-practice TR states that if performance is not an issue, aligning existing virtual machines may be more trouble than specifically worth.

Is there any way to guesstimate the performance delta between our specific, misaligned environment and a hypothetical, properly-aligned one?  That is, I would like to know how much of a hit the storage system is taking due to the mis-alignment, even if our users are not experiencing issues.

Thanks,

Eugene

[chriskranz]

If you go into "priv set diag" (warning: be careful!), you can run the stats command to show the misaligned block counts...

filer01*> stats list counters LUN
Counters for object name: LUN
        read_ops
        write_ops
        other_ops
        read_data
        write_data
        queue_full
        avg_latency
        total_ops
        scsi_partner_ops
        scsi_partner_data
        read_align_histo
        write_align_histo
        read_partial_blocks
        write_partial_blocks

This won't specifically tell you the performance overhead and hit you are having due to this, but it'll give you an idea of how much of your data is getting effected by misalignment.