Should I use RAID for backup? No.
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information. Yes, the answer kind of snuck out there. No,
you should not use RAID for backup. Here's the question, "Do
you think RAID is a valuable alternative for backing up?" The
answer is no. No, it just is not. I wanna review what RAID
is and more importantly, what it is not. RAID is an acronym
for redundant array of inexpensive disks or drives.
Using RAID technology, multiple disks are combined in various
ways to act or behave as if they were a single disk. There
are several ways that they can be arranged but there are
typically two reasons for duo or using RAID. One is
reliability and the other is speed. Those two sometimes
combined are the goal of having what's called a RAID array. So,
reliability, RAID one, which is what the question was actually
asking about, uses what's called mirroring. To improve
the reliability or more correctly the fault tolerance
of a disk drive. What happens is the two drives appear as if
they are one. When you write something, it gets written to
both drives. The reason that RAID One gives you reliability
is that either of those drives can fail. In fact, they can
fail completely and your system will keep working because
everything continues to be stored on the other drive. It
is not a backup but it is a redundant copy, a live
redundant copy of everything you're working on. Many
hardware RAID controllers actually allow you to replace
the failed drive without turning it off so that you can
basically keep running as if nothing happened. Once the
replacement drive is installed, the RAID controller takes care
of updating it with all of the data that's on the working
drive and then continues to write all the data to both as
it arrives. That's reliability. Throughout all of this, that
one logical drive, your C drive, for example, just
continues to work. RAID is also improved speed. So, RAID zero
uses what's called striping to increase the apparent speed of
your disk. What that means is that rather than writing your
data on one disk. It spreads it out across two disks. So, half
of your data is written on one disk and half of your data is
written on another. That sounds kinda nifty because what
happens is when you read the data, it can actually be read
twice as fast. It can start The first half of the data and the
second half of the data at the same time so that it arrives
more quickly to your computer CPU. The downside is that
you've doubled your chance of failure. If either disk fails,
you've now lost all of the data on both. There's no way to
recover the data on a failed drive if you're using something
like RAID Zero. That's why RAID zero honestly should never be
used It still is from time to time and I've even seen systems
come that way but it should never be used unless you've got
yourself one heck of a backup strategy because like I said,
you've got two disks, two chances for failure, either of
which will cause the entire disk to be lost. Now, we can
move on from RAID zero and RAID one into various combinations
which have various numbers and I'm not gonna try and lay out
all the different RAID combinations but if we take the
two concepts that we've just talked about. Writing the data
redundantly on two different drives and spreading the data
across two different drives. If we combine those, we actually
can get the best of both worlds. So, if we take three
drives, I'll call them A and B and Z. When data is written to
this trio of drives, A, B, and Z, A and B are treated kind of
like RAID one. In other words, they get a copy of the data but
at the same time, a calculation is performed. It's called a
check sum but you can think of it as a simple sum of just the
data that's written to A plus the data that's written to B is
what's then written to drive Z, the third drive in this trio.
So, what does that mean? Well, it means that either of those
drives. In fact, any of those drives can fail and everything
is recoverable. If drive A fails, well, you recalculate it
by Z minus B. If drive B fails, well, you recalculate what was
on it by Z minus A and of course, if drive Z fails, well,
you recalculate it as everything on A plus everything
on B. That's over simplified, of course, but the idea is that
anyone of those drives can fail, can be replaced without
any data loss and on top of that, the data is spread out
across those two drives. It's not duplicated, it's spread out
across those two drives which means it actually get faster.
The reads to that drive or even the rights to that drive can
often be significantly faster than writing to a simple drive.
This concept typically gets expanded beyond three drives.
Sometimes as many as five or seven or even more but the idea
is the same. Data is spread across some number of drives
and then there is an additional drive or drives that contain a
calculation that allows some combination of the data to be
recovered should any of the drives fail. So, all of this is
well and good and it kind of explains why rate exists.
Again, redundancy so that hardware can fail without data
loss and speed so that you have multiple drives sharing the
load reading off of it faster. It's not a backup. It's still
not a backup. The data is in only one place. It's in the
RAID array. If the RAID controller, which is a single
point of failure in this scenario happens to die and it
definitely happens. You've, once again, lost all of your
data and in fact, because the disks are behind the RAID
controller, it's usually the case that the data can't even
be recovered off the drives because they're in a
proprietary format unique to that specific RAID controller.
So, you still need to backup. RAID is great for redundancy,
for reliability, for performance, but it is not a
substitute for backup and finally, one last thing I wanna
point out about RAID RAID was developed and is at its best
when the drives you're talking about are running spinning
magnetic hard disk platters. They are the ones that have
speed issues relating to where the data might be stored on the
drive. They're slower than SSDs. While technically, you
could use an array of SSDs as a uh uh an arrayed array, it's
typically not done. Typically, rate arrays are really all
about spinning magnetic disks. Rate is great when it's for,
it's just not good for backups. If this kind of information is
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I'm Leo Notenboom. This is askleo.com. Thanks
for watching.