An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer
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He gets the acronym correct, at least, pointing out that "inexpensive" is what it really stood for.
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What's bizarre is skipping RAID 6. Like I know that this is simple, but it seems like so little to have skipped. Skipping weird stuff or rare stuff is one thing, but RAID 6 is so mainstream. It's like talking about American made cars and skipping Ford.
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@travisdh1 said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
Does CompTIA still say that hardware RAID is faster than software RAID?
Prof Messler said that hardware is "obviously faster". So not only did he repeat totally wrong information, he stated something as being "obvious" when common sense (and real world testing) says that it would "obviously" be the opposite of what he said. How could hardware RAID reasonably compete with software RAID? Makes no sense, not in performance anyway.
That's quite a shocking myth to not just repeat blindly (at least warn people that the A+ is wrong) but to add an "obviously" to try to make people feel foolish if they question it.
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I'm a little confused by this. If the OS can't see a hardware based RAID, what do you do with it? Also, is a desktop with 2 hard drives considered a RAID 0?
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@mary said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
I'm a little confused by this. If the OS can't see a hardware based RAID, what do you do with it?
OS sees the RAID, not the drives inside the RAID. No matter how many physical disks are in your RAID array, what the OS sees is a single virtual disk created from all of those physical ones being "RAIDed" together.
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@mary said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
Also, is a desktop with 2 hard drives considered a RAID 0?
No, RAID 0 is two (or more) disks that are striped and presented as a single disk. Two drives in a desktop are neither striped nor abstracted into a single storage unit.
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@scottalanmiller said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
@mary said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
Also, is a desktop with 2 hard drives considered a RAID 0?
No, RAID 0 is two (or more) disks that are striped and presented as a single disk. Two drives in a desktop are neither striped nor abstracted into a single storage unit.
wouldn't RAID 0 also be considered "Mirrored" Raid?
I know that's what we use for our "Servers"
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@WrCombs said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
@scottalanmiller said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
@mary said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
Also, is a desktop with 2 hard drives considered a RAID 0?
No, RAID 0 is two (or more) disks that are striped and presented as a single disk. Two drives in a desktop are neither striped nor abstracted into a single storage unit.
wouldn't RAID 0 also be considered "Mirrored" Raid?
I know that's what we use for our "Servers"
No, RAID 0 is striping. RAID 1 is mirroring. They are opposites in every way.
RAID 0 has no redundancy, it requires all disks, if any fail, all is lost. RAID 1 is all redundancy, no matter how many disks you have, all but one can fail and nothing is lost.
RAID 0 is more dangerous than no RAID at all, the bigger the array the more dangerous it is. RAID 0 is "intentionally putting data at risk." It is only for ephemeral uses where data stored there doesn't matter.
RAID 1 is the safest of all RAIDs. The bigger the array the safer it is. It is for the data that matters the most.
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A mirror means that data is copied to all members of the array. So if you have one byte of data, and four disks in a mirror set, you have that same byte copied for times.
A stripe means that a single piece of information is broken up. If you have one byte of data in a four disk stripe, each disks gets just 1/4 of the byte. If any disk fails, you can't put the byte back together again.
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@scottalanmiller said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
@WrCombs said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
@scottalanmiller said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
@mary said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
Also, is a desktop with 2 hard drives considered a RAID 0?
No, RAID 0 is two (or more) disks that are striped and presented as a single disk. Two drives in a desktop are neither striped nor abstracted into a single storage unit.
wouldn't RAID 0 also be considered "Mirrored" Raid?
I know that's what we use for our "Servers"
No, RAID 0 is striping. RAID 1 is mirroring. They are opposites in every way.
RAID 0 has no redundancy, it requires all disks, if any fail, all is lost. RAID 1 is all redundancy, no matter how many disks you have, all but one can fail and nothing is lost.
RAID 0 is more dangerous than no RAID at all, the bigger the array the more dangerous it is. RAID 0 is "intentionally putting data at risk." It is only for ephemeral uses where data stored there doesn't matter.
RAID 1 is the safest of all RAIDs. The bigger the array the safer it is. It is for the data that matters the most.
I got the 2 mixed up
We use RAID 1 - thanks for explaining. -
Is it true hardware is faster when using raid5/6 due to the fast onboard cache on the hardware that would speed up those operations? Or does software raid use system ram for that which I'm just assuming is even faster than that? How does it work VS the other in this case?
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@Obsolesce said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
Is it true hardware is faster when using raid5/6 due to the fast onboard cache on the hardware that would speed up those operations? Or does software raid use system ram for that which I'm just assuming is even faster than that? How does it work VS the other in this case?
No, hardware is not faster. Both systems have cache. Software can have way bigger and faster cache, though, and way bigger and faster CPU. In both cases, you CAN limit available CPU and turn off cache. But the best hardware cards have small caches and CPUs that only get "closer" to normal CPUs. Even the lowest end server will have way more CPU power and tons more RAM available for cache for the RAID system
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@scottalanmiller said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
@Obsolesce said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
Is it true hardware is faster when using raid5/6 due to the fast onboard cache on the hardware that would speed up those operations? Or does software raid use system ram for that which I'm just assuming is even faster than that? How does it work VS the other in this case?
No, hardware is not faster. Both systems have cache. Software can have way bigger and faster cache, though, and way bigger and faster CPU. In both cases, you CAN limit available CPU and turn off cache. But the best hardware cards have small caches and CPUs that only get "closer" to normal CPUs. Even the lowest end server will have way more CPU power and tons more RAM available for cache for the RAID system
@scottalanmiller said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
@Obsolesce said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
Is it true hardware is faster when using raid5/6 due to the fast onboard cache on the hardware that would speed up those operations? Or does software raid use system ram for that which I'm just assuming is even faster than that? How does it work VS the other in this case?
No, hardware is not faster. Both systems have cache. Software can have way bigger and faster cache, though, and way bigger and faster CPU. In both cases, you CAN limit available CPU and turn off cache. But the best hardware cards have small caches and CPUs that only get "closer" to normal CPUs. Even the lowest end server will have way more CPU power and tons more RAM available for cache for the RAID system
That was my question, if software raid generally or always uses system ram for caching the same concept as hardware raid uses it's onboard cache?
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@Obsolesce said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
That was my question, if software raid generally or always uses system ram for caching the same concept as hardware raid uses it's onboard cache?
Like hardware RAID, it is an option. But any enterprise software RAID will offer that, of course. Just like hardware RAID, if it doesn't have cache, it's not really production ready
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Is using a RAID 1 configuration faster as well? Or is its main purpose so if you lose one of the drives you have a backup?
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@connorsoliver said in An Overview of RAID - CompTIA A+ 220-901 220-902 Video Training by Prof. Messer:
Is using a RAID 1 configuration faster as well? Or is its main purpose so if you lose one of the drives you have a backup?
Primary purpose is definitely data protection. But RAID 1 provides a 200% read performance benefit over using a single drive. Write performance is the same as a single drive.
