Storage Integrity (Demo)
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Video Transcription
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>> Hey Cybrarian, and welcome back to
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the Linux+ course here at Cybrary,
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I'm your instructor Rob Goelz.
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In today's lesson, we're going to
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be covering Storage Integrity.
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Upon completion of today's lesson,
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you're going to be able to understand the types of
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storage integrity issues that
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you may need to troubleshoot,
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as well as use commands to find
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degraded storage or identify bad blocks.
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Now, strictly speaking on the Linux+ exam,
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storage integrity refers to bad blocks,
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that are identified on a storage device
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or maybe on a partition.
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However, the storage itself can become degraded.
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This can refer to the storage medium,
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such as on a SSD,
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which has a limited number of read and write,
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or what are called program or erase, PE cycles,
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but it could also refer to a degraded mode,
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which is when one or more disks
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in a RAID array have failed.
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Let's look at degraded storage first.
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If we have SMART on a storage medium,
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smartctl can be used along with
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any other vendor-provided attributes
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to determine the wear on that device.
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We'll talk a little bit more
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about that in the next slide.
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But if we're troubleshooting a RAID device
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that's maybe degraded,
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the easiest way to see this is with the mdadm command.
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We could use mdadm-D,
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and then the RAID array,
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and it's going to display the detailed
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status information about that array.
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Now, if we see the word degraded in the status return,
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that means that there is an issue on that RAID device.
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When we're testing for bad blocks on a device,
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we can use that bad blocks command.
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For example, we could run this on,
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say /dev/sdb1, but,
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of course, we need to do is after unmounting.
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What we're going to do after we've
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unmounted /dev/sdb1 is we can run
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sudo bad blocks-nsv on /dev/sdb1.
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What that's going to do is going to do
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a non-destructive read-write test
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for bad blocks on that device,
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and it's going to check all blocks
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from zeros to the end,
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and perform its nondestructive read-write test,
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and then if it pass successfully down to the bottom,
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we're going to see pass completed
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and zero bad blocks found.
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Otherwise we would see the error message here,
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you can see is 0/0/0 errors.
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You would see errors incremented in
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that very last part there in between the parentheses.
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Now another way to check for
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bad blocks is to use smartctl.
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We can use smartctl-a, and then the name of the device.
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This is going to display unreadable disk sectors as
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either currently pending or offline uncorrectable.
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Now, keep in mind, a block
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is actually a group of sectors.
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It may be one, or several bad
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sectors that are causing the bad blocks.
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In this lesson, we covered the types of
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storage integrity issues that
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you may need to troubleshoot,
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and then we talked about using commands to
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identify degraded storage and bad blocks,
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such as smartctl,
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mdadm, and badblocks.
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Thanks so much for being here and I look
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forward to seeing you in the next lesson.
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