I'd like to do some general disk io monitoring on a debian linux server. What are the tools I should know about that monitor disk io so I can see if a disk's performance is maxed out or spikes at certain time throughout the day?
For disk I/O trending there are a few options. My personal favorite is the
sar command from
sysstat. By default, it gives output like this:
09:25:01 AM CPU %user %nice %system %iowait %steal %idle 09:35:01 AM all 0.11 0.00 0.01 0.00 0.00 99.88 09:45:01 AM all 0.12 0.00 0.01 0.00 0.00 99.86 09:55:01 AM all 0.09 0.00 0.01 0.00 0.00 99.90 10:05:01 AM all 0.10 0.00 0.01 0.02 0.01 99.86 Average: all 0.19 0.00 0.02 0.00 0.01 99.78
%iowait is the time spent waiting on I/O. Using the Debian package, you must enable the stat collector via the
/etc/default/sysstat config file after package installation.
To see current utilization broken out by device, you can use the
iostat command, also from the sysstat package:
$ iostat -x 1 Linux 3.5.2-x86_64-linode26 (linode) 11/08/2012 _x86_64_ (4 CPU) avg-cpu: %user %nice %system %iowait %steal %idle 0.84 0.00 0.08 1.22 0.07 97.80 Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util xvda 0.09 1.02 2.58 0.49 112.79 12.11 40.74 0.15 48.56 3.88 1.19 xvdb 1.39 0.43 4.03 1.82 43.33 18.43 10.56 0.66 112.73 1.93 1.13
Have a look at iotop.
Or iodump, if that's more down your way of thinking.
Note: This requires at least kernel 2.6.20 to work.
dstat. It can show totals and statistics per disk and even md-devices (RAID), also can use colors for better overview:
$ dstat -tdD total,sda,sdb,sdc,md1 60 ----system---- -dsk/total----dsk/sda-----dsk/sdb-----dsk/sdc-----dsk/md1-- time | read writ: read writ: read writ: read writ: read writ 08-11 22:08:17|3549k 277k: 144k 28k: 851k 62k: 852k 60k: 25k 82k 08-11 22:09:17| 60k 258k:1775B 15k: 13k 63k: 15k 60k: 68B 74k 08-11 22:10:17| 176k 499k: 0 14k: 41k 122k: 41k 125k: 273B 157k 08-11 22:11:17| 42k 230k: 0 14k:9830B 54k: 14k 51k: 0 70k 08-11 22:11:52| 28k 132k: 0 5032B:5266B 33k:9479B 28k: 0 37k
-dfor disk statistics
-Dto specify the exact devices to report
60to average over 60 seconds. The display is updated every second, but only once per 60 seconds a new line will be started.
not used in this example, but
-ccan report wait IO percentage, which in most cases is related to the CPU waiting for data from the disks.
It is available for most Linux distributions, but sometimes needs to be installed from repositories.
Just from files on your computer (assuming a recent kernel) you can ask
/proc/diskstats. It will need some translating, however. But it's nice for a quick and dirty check.
Another option is to use:
sudo iotop -aoP
-a Will show accumulated output -o Will only output -P Will only show processes instead of threads
This program will tell you how much a process has written to disk and read from disk since iotop was started.
Monitoring Disk Io can be done by multiple tools like the following.
Also some important operating system concepts are very much necessary to comprehend them..read the Linux IO complete tutorial
Another great tool for a quick overview where the load comes from is
It can show you an overview over all resources (CPU, memory/swap, network and disk I/O) or you can drill down to a single resource and sort processes by how much they consume.
Why not try nmon. It does disks and network with processes. Originally for AIX but it has been ported to Linux for some years now.