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Storage issues are quite common

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when working on any operating system.

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Some of the most common ones are missing devices, volumes,

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mount points, denigrated storage,

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performance issues and more.

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So, I'm going to walk you through a couple commands

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to identify performance issues as well as optimize storage.

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The first set of commands we're going to walk

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through is the disk free command.

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Now we see it just lists all the different storages

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that we have, blocks, use, available, et cetera.

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Now, there's another option here.

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The "H" stands for human readable,

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so it makes it a lot more user friendly.

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Now we see similar information

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but just in a better format for us.

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Now, we also filter the results to a more specific device.

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So in this example, we're going to use

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the backup system that we created prior.

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So we're going to do disk free human readable

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for the backup system and we use the data one.

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Okay.

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Again, the clean view of the statistics

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of the particular storage device.

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So that's problem, we're going to also go

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through the disk usage command.

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Now this command, since had a lot of information

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so we just want to look at it real quick.

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So it gives pretty much the use of every drive.

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So we need to specify this, so we want to do sudo.

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We're going to use our same folder from earlier.

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And again, this is a very clean way of viewing disk usage.

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Might be more useful in our particular situation too.

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I actually use the whole folder.

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So we do it that way.

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We just get quick clean view

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of how much information is being used.

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Now, the next command we're going to go

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over is the input output stat.

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Now, this command's going to give us rewrite statistics

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of the particular volume that we're looking at.

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So first we're going to use, instead

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we're going to use the backup again, just for this example

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we're just going to keep using the data one.

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For the first set, we're going to go

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through transactions for a second.

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The read speed, the write speed, the total amount

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of kilobytes read and total amount kilobytes written.

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Now, the best thing to do is compare it

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'cause it's kind of hard unless you know a good baseline

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of how fast it typically moves.

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So, usually you have to view this over time and to see

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if there's any huge difference between these values.

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So another command that's very useful is using

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the input output ping command.

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Now, it lets us track latency in real time.

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So, we're going to use for this example and put

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out the ping use, okay, we're going to use account four.

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If not, it'll be unlimited.

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You want to use backup system and the data back.

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Okay, and of course, similar to the ping,

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it lets us know how long it's taking per request.

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So again, once we get a good baseline, we can tell

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if there's any issues, if it's a lot slower than normal,

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you'll see those values are a lot higher.

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Another Linux current process is scheduling.

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Now this is very important for optimization

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because there'd be scenarios where we don't want

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to treat every request the same.

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So, the system prioritizes certain requests over others

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to minimize performance issues.

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Now there's three primary ways

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to do this type of scheduling.

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There's a deadline, CFQ which stands

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for complete fair queuing and the NOP one,

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which stands for just no input output.

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So pretty much there's no priority on anything.

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Now, the no input output one, NOP is very useful

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for the scenario when we're using flash drives

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and modern hard drives because those systems typically

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have their own scheduling built into the controller

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and not rely on the current to make those decisions.

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So, we're going to use an example really quick

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and let's just view the current value

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of the schedule that we currently have.

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Now, the one that's in the brackets is the one

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that's currently set.

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So for this system, we have the deadline one set.

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Now we're just going to change this

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and it's going to be a simple echo command,

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but I'm going to switch to root first.

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Okay, now that I'm root, we're going to switch this scheduler

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to the no op configuration, it'd be simple little echo.

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I'm going to do no op.

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I'm going to go to the sys.

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Block, sda, queue, scheduler.

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Okay, command went through successfully.

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Again, just to view, make sure that went through.

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Again, the one in the bracket is going to identify

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the selected scheduler type.

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Sometimes we're going to run into issues where a device

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or typically a user is using excessive storage consumption.

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So we're going to walk through how this set quoters on a user.

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We're going to edit the fstab file.

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Again, that's what the current users

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at boot to understand what's going

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on within the file system.

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So we need to let it know that, Hey, look,

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we want to make sure that we have a quota

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on this particular backup system.

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So that's what we're typing in here.

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That's the mount point.

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That's the file system.

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And keeps on default setting and we're going to use user quota.

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Okay, great.

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Right click there.

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Okay.

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Now we'll have to remount the system.

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The "O" just stands for options,

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just letting the system know

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that there'll be options to follow.

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I'm going to use the remount.

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Okay.

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The command we're going to use to configure the user quotas

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for the data backup file system is quota check.

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We're going to use the options CUGM.

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The "C" means create new files,

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don't worry about anything that's existing.

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And the "U" and the "G" stands for users

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and groups that are part of the file system.

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And the "M" just lets us know not

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to remount this cause we've already done that prior.

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Okay.

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Next thing we need to do is actually turn

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on the check system and the "-A" stands

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for all file systems.

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Now this example, we're going to use a user I created J Snow.

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He's a pesky user, he's been using too much data.

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So we need to watch in real time how we're able

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to start putting information into the backup data system

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and how it cuts it off as the user goes

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above the soft and hard limits.

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So, what we need to do is edit the quota for John Snow.

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We're going to use the ed quota quota command.

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So we're going to identify the user.

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Again, we're going to use J snow in this example, the VM.

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So we're going to use I for insert, sorry.

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Here we're going to edit this soft limit

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of 10,000, 2,000 blocks.

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Put it to hard, 15,000.

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Keep this the same, 500 here.

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700 here.

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Now what we just changed was the soft and hard limits

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for the blocks that the user is allowed to use

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and all the way to the right, it's the soft and hard limits

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for the files specifically that the user stores.

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So, I'm get out of here and save this.

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Now in a second, we're going to switch

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to J Snow and we're going to actually input some data

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into that backup data system.

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So we need to actually make sure he has the

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proper permissions to do such things.

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So we're going to do the change model really quick

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to this backup system, just to make sure.

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Okay.

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Now let's switch to J Snow.

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All right, now we're going to use the DD command

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which is a copy command and pretty much it's just saying

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we're going to copy from a file that's the IF

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and it's going to be the dev zero file.

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This is just a dummy file,

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so don't worry too much about that.

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We're going to output to a file and this file is going

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to be the backup system that we created in the data folder.

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We're going to name it "My file".

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We're going to give it a value of one megabyte

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and we're going to do this five times.

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Okay?

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Now again, if you're not familiar with this

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we're going to list out what just happened here.

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So if you see at the bottom, we see

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the "my file" was created and it's roughly 5 million bites.

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Again, just a quick way

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to make the demonstration go smoothly.

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Now let's exit out of here 'cause we need

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to use pseudo commands to check out this report.

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So we're going to check out the report for the quota.

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The backup system.

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And now we can see it list out

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John has used roughly 5,000 blocks.

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He has a limit of 10,000, but his hard limit is 15,000.

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Now let's switch back to John.

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And we're going to do this one more time.

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This time we're going to create another file

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and we're going to make do this seven times, okay?

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Just double check that they went through properly.

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We'll see the second file was created,

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roughly 7 million bytes.

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Now let's check this report again.

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See how the information has changed.

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Now we see J Snow has used roughly 12,000 blocks,

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an example exceeding this soft block limit threshold.

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So you see that grace period is now counting

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down from the seven days.

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And again, if he does not reduce the amount used

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within the seven days, he will not be able

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to store any more information into that file system.

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And if he goes above the hard limit,

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he will also be cut off.

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Now, if you've guessed, we're going to switch back to John

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and we're going to do this one final time,

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just to see this in action.

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We're going to create another file

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and we're going to try to do this 10 times

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and we should get an error here.

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Now, if you look, you will see error writing

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that this quota was exceeded.

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So, what happens is the system identifies

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that J Snow was trying to use too much data

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so it will cut him off, it's not going to allow him

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to go above that hard limit.

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So once we do this quota report again,

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we'll see the cutoff happen.

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Again, it didn't allow him to use more than the hard limit.

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So we see this process is effective

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and it works in real time.

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Now thank you for sticking with me through this walkthrough

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and I'll see you in the next lesson.