Lustre Monitoring and Statistics Guide

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DRAFT IN PROGRESS

Introduction

There are a variety of useful statistics and counters available on lustre servers and clients. This is an attempt to detail some of these statistics.

The presumed audience for this is system administrators attempting to better understand and monitor their lustre file systems.

Lustre Versions

This information is based on working mostly with lustre 2.4 and 2.5.

Reading /proc vs lctl

'cat /proc/fs/lustre...' vs 'lctl get_param' With newer lustre versions, 'lctl get_pram' is the standard and recommended way to get these stats. This is to insure portability. I will use this method in all examples, a bonus is it can be often be a little shorter syntax.

Data Formats

Format of the various statistics type files varies (and I'm not sure if there is any reason for this). The format names here are entirely *my invention*, this isn't a standard for lustre or anything.

It is useful to know the various formats of these files so you can parse the data and collect for use in other tools.

Stats

What I consider a "standard" stats files include for example each OST or MDT as a multi-line record, and then just the data.

Example:

obdfilter.scratch-OST0001.stats=
snapshot_time             1409777887.590578 secs.usecs
read_bytes                27846475 samples [bytes] 4096 1048576 14421705314304
write_bytes               16230483 samples [bytes] 1 1048576 14761109479164
get_info                  3735777 samples [reqs]

snapshot_time = when the stats were written

For read_bytes and write_bytes: First number = number of times (samples) the OST has handled a read or write. Second number = the minimum read/write size Third number = maximum read/write size Fourth = sum of all the read/write requests in bytes, the quantity of data read/written.

Jobstats

Jobstats are slightly more complex multi-line records. Each OST or MDT also has an entry for each jobid (or procname_uid perhaps), and then the data.

Example:

obdfilter.scratch-OST0000.job_stats=job_stats:
- job_id:          56744
  snapshot_time:   1409778251
  read:            { samples:       18722, unit: bytes, min:    4096, max: 1048576, sum:     17105657856 }
  write:           { samples:         478, unit: bytes, min:    1238, max: 1048576, sum:       412545938 }
  setattr:         { samples:           0, unit:  reqs }  punch:           { samples:          95, unit:  reqs }
- job_id: . . . ETC

Notice this is very similar to 'stats' above. But there's a lot of extra: { bling: }! Why? Just because it got coded that way?

Single

These really boil down to just a single number in a file. But if you use "lctl get_param" you get an output that is nice for parsing. For example:

[COMMAND LINE]# lctl get_param osd-ldiskfs.*OST*.kbytesavail


osd-ldiskfs.scratch-OST0000.kbytesavail=10563714384
osd-ldiskfs.scratch-OST0001.kbytesavail=10457322540
osd-ldiskfs.scratch-OST0002.kbytesavail=10585374532

Histogram

Some stats are histograms, these types aren't covered here. Typically they're useful on their own without further parsing(?)


  • brw_stats
  • extent_stats

List of stats

This is a collection of various stats files that I have found useful. It is *not* complete or exhaustive. Additions or corrections are welcome.

host type, target, format, discussion

  • Host Type = MDS, OSS, client
  • Target = "lctl get_param target"
  • Format = data format discussed above
Host Type Target Format Discussion
MDS mdt.*.job_stats jobstats Metadata jobstats. Note that with lustre DNE you may have more than one MDT, so even if you don't it may be wise to design any tools with that assumption.
OSS obdfilter.*.job_stats jobstats the per OST jobstats.
MDS mdt.*.md_stats stats Overall metadata stats per MDT
MDS mdt.*MDT*.exports.*.stats (SCOTT, VERIFY THAT..) stats Per-export metadata stats. Exports are clients, this also includes other lustre servers. The exports are named by interfaces, which can be unweildy. See "lltop" for an example of a script that used this data well. The sum of all the export stats should provide the same data as md_stats, but it is still very convenient to have md_stats, "ltop" uses them for example.
Example Example Example Example
Example Example Example Example
Example Example Example Example
Example Example Example Example
Example Example Example Example