added md disks in down state

[Finomosec]

Added missing mdadm stats:

• node_md_disks # added {state="down"}
• node_md_sync_time_remaining (seconds)
• node_md_blocks_synced_speed
• node_md_blocks_synced_pct

Notes:

• One drive was not being shown, as it was in state="down" (recovering), which was not reported in the output.
• Using node_md_blocks_synced / node_md_blocks as progress percentage created wrong results on my system, as the total-blocks differed from the total-to-be-synced-blocks. This may be due to the raid-level being used (raid5).

md0 : active raid5 sdf1[4] sde1[1] sdc1[2] sdb1[0]
      14650718208 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/3] [UUU_]
      [===================>.]  recovery = 99.9% (4882207424/4883572736) finish=7.8min speed=2908K/sec
      bitmap: 2/37 pages [8KB], 65536KB chunk

[Finomosec]

@SuperQ
I'm done for now.
Feel free to merge it at any time.

[SuperQ]

This doesn't seem necessary, we should be able to compute this from something like rate(node_md_blocks_synced[1m]) * <blocksize>.

Suggested change

	blockSyncedSpeedDesc = prometheus.NewDesc(
	prometheus.BuildFQName(namespace, "md", "blocks_synced_speed"),
	"current sync speed (in Kilobytes/sec)",
	[]string{"device"},
	nil,
	)

[Finomosec]

I think it is usefull. It is the CURRENT speed, as it is shown in /stat/proc/mdstat
I have it showing in my Grafana board.
Plus i guess <blocksize> is not included in the data, so it would require additional configuration for each md-device.

[Finomosec]

My Grafana Board: https://grafana.com/grafana/dashboards/20989-node-exporter-mdadm-status/

[dswarbrick]

Note that the groundwork has already been laid for #1085, and we probably should not add any new parsing functionality relating to /proc/mdstat.

[SuperQ]

Maybe instead of exposing the sync percent, we should expose the "TODO" blocks value. This way the completion ratio can be correctly calculated as node_md_blocks_synced / node_md_blocks_synced_todo.

[Finomosec]

Maybe instead of exposing the sync percent, we should expose the "TODO" blocks value. This way the completion ratio can be correctly calculated as node_md_blocks_synced / node_md_blocks_synced_todo.

That was my first idea, too, but the data-source (https://github.com/prometheus/procfs/blob/master/mdstat.go) does not (yet) capture/expose this value.

Also node_md_blocks_synced_todo is not a good name. todo sound like remaining, which is not correct.
Maybe to_be_synced would suffice.

But hey! We could calculate it using blocks_synced and the percentage.
What do you think, should we do this?

... but it might be imprecise, especially for low percentage values plus it might yield slightly different results over time, which would be kind of akward.

So maybe better not after all.

I added a request to add it:
prometheus/procfs#636

[discordianfish]

Yeah I agree, let's add the TODO blocks to procfs

[SuperQ]

Released updated procfs: https://github.com/prometheus/procfs/releases/tag/v0.15.0