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mikeymike
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People who say "RAID1 is not a backup"

Thu Apr 14, 2011 7:59 am

I've just read a thread where someone came out with this. I'm sorry, but I think people who think this need to be corrected.

Backup systems take many forms because a backup system can perform some functions and not necessarily others. If someone wants a backup system, I ask the question: Are you looking for protection against, for example, a hardware failure, and/or are you looking for protection against accidental edits/deletions?

A RAID1 setup that covers some data that you wouldn't like to lose is a good thing. It is a backup system to protect against the possibility of a sudden hard disk failure. As someone rightly pointed out on another thread, it doesn't protect against data corruption (like say Word mangling a precious document).

However, if you're looking for protection against accidental edits/deletions or file corruption, you should look elsewhere. You might want to have RAID1 and another backup system alongside it, it depends how much you want to protect yourself from potential risks and possibly how much you want to spend.
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 8:17 am

RAID1 was designed for uptime. Uptime is different than backup.
Because of this, RAID1 was not designed for backup.
Because of this, people say 'RAID1 isn't for backup.'
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 8:23 am

The reason people say this is to counter the very large contingent of people who apparently believe that a RAID-1 setup is the *only* "backup" you need. RAID-1 only protects you against a small subset of all the possible events which can result in permanent data loss. RAID is really more about system availability than data security, in that it minimizes (or completely eliminates if you have hot-swap capable drive bays) downtime in the event of a disk failure.

Whether you're using RAID or not, any data you can't afford to lose still needs to be backed up to external/removable media... and preferably stored off-site. Period.

And that's what people are getting at when they say "RAID is not a backup".
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 8:28 am

You're just redefining what backup means, by defining it down. No go.

The reason everyone harps on this is because people are constantly losing data they falsely thought to be safe. We're strict about what it means because we're tying to help people.

People who think they've made a "backup" of their data whenthey copied it somewhere else on the same physical drive, so when the harddrive goes they're shocked.

People who think they've made a "backup" by manually putting their files on two different harddrives in the same computer, only to have them both fried when their house gets hit by lightning.

People who think they've have a backup because they save their work locally and on a network drive, but during their work process they routinely save to both locations. Then they wonder if we can revert to a previous version, but the server only did weekly backups, not daily incrementals. A day wasted manually undoing what they did.

All of these, by the way, are real situations I've seen in my life.
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 8:31 am

If a power surge wipes out your drives, both are going to die and therefore you have no backup.

Backup is usually designated by as either offsite or you have the ability to take it off site should you choose. External USB drive, tape, cloud storage backup, DVDs, etc.
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 8:34 am

Your data's not backed up unless it'd take a nuclear war to destroy it. A copy in another state! :wink:
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 8:41 am

grantmeaname wrote:
RAID1 was designed for uptime. Uptime is different than backup.
Because of this, RAID1 was not designed for backup.
Because of this, people say 'RAID1 isn't for backup.'


I'm not sure if you're trying to express your opinion or explain what other people think. Just because something was designed for a purpose, it doesn't necessarily mean it can't serve any other purpose.

@ just brew it!

I agree with what you're saying.

@ Glorious

So you don't think that RAID1 provides a safety net in the event of a disk failure? Of course it's a form of backup.

I've encountered the same situations you've described too. However, each "backup" you describe is actually a backup, just because the person using that method isn't properly aware of the shortcomings of that system (and/or not being sensible about how they store their data in the first place), doesn't make it not a backup system.

The most common scenario I encounter is when a customer thinks they've protected their photos from loss by moving them off their computer and on to a memory stick :)

@ Corrado

Yes, RAID1 is not the be-all and end-all of backup systems.

@ bthylafh

Well pointed out :)
Last edited by mikeymike on Thu Apr 14, 2011 8:45 am, edited 1 time in total.
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 8:44 am

bthylafh wrote:
Your data's not backed up unless it'd take a nuclear war to destroy it. A copy in another state! :wink:

Why stop there? You really ought to store your backups off-planet. I think someone needs to figure out how to store data in a parallel dimension, so that it will remain unaffected even if the LHC causes the fabric of space-time to unravel! :wink:
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 8:48 am

Can we get into a RAID 5 vs RAID 10 discussion too? Those are fun!
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 8:54 am

mikeymike wrote:
So you don't think that RAID1 provides a safety net in the event of a disk failure? Of course it's a form of backup.


It is a safety net. No, it is not a backup.

mikeymike wrote:
I've encountered the same situations you've described too. However, each "backup" you describe is actually a backup, just because the person using that method isn't properly aware of the shortcomings of that system (and/or not being sensible about how they store their data in the first place), doesn't make it not a backup system.


And why do you suppose people aren't "properly aware" of the shortcomings?

This is why we are so strict about what the word backup means: Because calling everything a backup leaves regular people unaware of the differences!

People often don't get religion about proper backups until they've been bitten, often badly. We to fight indifference *and* ignorance, and using the same word for everything makes it even harder.
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 8:55 am

5150 wrote:
Can we get into a RAID 5 vs RAID 10 discussion too? Those are fun!


I prefer RAID5 to RAID10, if only because it's more flexible in setup. RAID10 is going to require drives in multiples of 4 (I think; it might be exponential. I've never investigated more than 4 drives for RAID10 before) RAID5 can take any number of drives from 3 to ∞+1.
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 8:55 am

RAID on a consumer PC is just a way for geeks to show-off that they know how to actually configure their hardware. It is rarely a needed feature. Kind of like overclocking a GPU, sure you can do it and it does have some benefits, but it also has drawbacks which are frequently ignored. Anyway, you really should know what each type of RAID does.

RAID0 - speed due striping, but also increased risk of data loss due to the increased likelihood of a drive failure as more drives are added.
RAID1 - Uptime and some slight speed increases when reading. Generally wasteful of resources. If you are going to duplicate all of your data it makes more sense for that second drive to be somewhere else.
Software RAID5/6 - No speed benefit due to dependence on CPU for parity calculations. It can assist in uptime, but a crippled software RAID5/6 runs like tar. In addition, you have the chance of being unable to rebuild an array due to hardware incompatibilities - a new risk. So if the MB or cheapo add-in card gets fried you might need to get the exact same SKU - which could be a problem a couple years down the line. Serious headaches expanding an array (if possible). I really don't understand the desire for this option.
Hardware RAID5/6 - Speed, uptime, expandability, hot spares - and boy do you pay for it. Don't forget to get the battery attachment for these cards because you don't want writes to be interupted by unforeseen circumstances. These really belong only on servers, but if you have idle cash - knock yourself out.
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 8:59 am

mikeymike wrote:
So you don't think that RAID1 provides a safety net in the event of a disk failure? Of course it's a form of backup.

I've encountered the same situations you've described too. However, each "backup" you describe is actually a backup, just because the person using that method isn't properly aware of the shortcomings of that system (and/or not being sensible about how they store their data in the first place), doesn't make it not a backup system.

The issue is that they are poor forms of backup, which give people who don't know any better a false sense of security.

Yes, claiming that RAID-1 "isn't backup" may be part hyperbole; but it is more right than wrong. The intent is to get people to actually think about their misconceptions regarding RAID in general.
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 9:07 am

mikeymike wrote:
I've just read a thread where someone came out with this. I'm sorry, but I think people who think this need to be corrected.

Backup systems take many forms because a backup system can perform some functions and not necessarily others. If someone wants a backup system, I ask the question: Are you looking for protection against, for example, a hardware failure, and/or are you looking for protection against accidental edits/deletions?

A RAID1 setup that covers some data that you wouldn't like to lose is a good thing. It is a backup system to protect against the possibility of a sudden hard disk failure. As someone rightly pointed out on another thread, it doesn't protect against data corruption (like say Word mangling a precious document).

However, if you're looking for protection against accidental edits/deletions or file corruption, you should look elsewhere. You might want to have RAID1 and another backup system alongside it, it depends how much you want to protect yourself from potential risks and possibly how much you want to spend.


Sorry, but I think that people who think what you think need to be corrected :wink:

RAID1 is not a backup. RAID1 is hardware redundancy. The point is to increase performance and reduce the chance of data loss due to hardware failure. If something happens to your machine that affects both drives - a power surge that kills both drives, destructive malware, or a stupid user with too much access - your data is lost. Lost is lost.

The purpose of a backup is to provide an additional copy whenever data is lost; regardless of why or how the data was lost.
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 9:07 am

Let us look at the main forms of disaster and go through them, to see if RAID 1 covers them:

- Single hard disk failure - YES
- Multiple drive failure (i.e. PSU fries system) - NO
- Silent data corruption - NO
- Accidental deletion/edit - NO
- Fire/theft - NO

So yeah, it's pretty weak as a "backup", and that's why we say that it isn't :)
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 9:09 am

With backups we talk in data sets. Let me repeat, data sets. We're talking entire sets of data. Again, data sets. RAID does not offer data sets. It offers real-time data redundancy or parity. There is a world of difference.

And as someone who has rebuilt RAID arrays hit by lightning, I can tell you what mcnabney says is the truth. Try finding an identical eight year old Dell PERC card, a 15GB harddrive the PERC card can see, figuring out which order the drives went in, which drive ate the surge and needs to be replaced, then realizing the server motherboard is fried so you have to put the RAID card in a separate PC and use a long SCSI cable from the PC to the server RAID array and boot the RAID array before the PC so it'll show up as a secondary drive. I beat it, though. I beat it! Muahahaha! That's no backup, that's a nightmare.
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 9:12 am

mcnabney wrote:
Software RAID5/6 - No speed benefit due to dependence on CPU for parity calculations. It can assist in uptime, but a crippled software RAID5/6 runs like tar. In addition, you have the chance of being unable to rebuild an array due to hardware incompatibilities - a new risk. So if the MB or cheapo add-in card gets fried you might need to get the exact same SKU - which could be a problem a couple years down the line. Serious headaches expanding an array (if possible). I really don't understand the desire for this option.

RAID-5 still has a significant speed benefit for reads; for applications where the majority of accesses are reads, the mediocre write performance may not be an issue (and with modern CPUs write performance of software RAID-5 isn't that bad). Hardware incompatibilities are not an issue if you use your OS's RAID-5 implementation instead of the one in the motherboard/controller vendor's drivers.

IMO the "write hole" issue is the main concern with RAID-5...
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 9:12 am

For my own personal use, raid1 probably would serve better than backups since drive failures have been the only situation I've ever experienced, although I currently just copy files to an external drive. Being hit by lightning is a laughable argument nowadays with PSU's having surge protection built in, and most people aren't using expensive hardware raid cards.
What's the best backup method for bringing your system back from the dead if you experience a drive failure? Whole drive backups/restoring take forever, and I'd like to know if there is a speedier way of doing them other than raid1.
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 9:19 am

l33t-g4m3r wrote:
For my own personal use, raid1 probably would serve better than backups since drive failures have been the only situation I've ever experienced, although I currently just copy files to an external drive. Being hit by lightning is a laughable argument nowadays with PSU's having surge protection built in, and most people aren't using expensive hardware raid cards.

The surge protection of a PC PSU (or even an external "surge strip") isn't going to protect you from a lightning strike.

What's the best backup method for bringing your system back from the dead if you experience a drive failure? Whole drive backups/restoring take forever, and I'd like to know if there is a speedier way of doing them other than raid1.

Preservation (or quick restoration) of functionality following a single drive failure is *exactly* what RAID is about. So either use RAID-1, or just deal with the time required to restore from a backup image. You can speed up the restoration process by using an eSATA or USB3 backup drive instead of USB2.
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 9:21 am

l33t-g4m3r wrote:
Being hit by lightning is a laughable argument nowadays with PSU's having surge protection built in, and most people aren't using expensive hardware raid cards.

Yes, I'm sure a PSU's surge suppression circuitry will stop a lightning strike. :roll:
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 9:25 am

This is a little off-topic, but RAID definitely hinders data recovery. If you have no backup and your hard drive fails, there's a good chance you can recover some or all of the data on that drive, expensive as such an exercise might be. Adding a RAID array to that calculation makes the odds of recovery much lower and the cost much higher.
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 9:27 am

just brew it! wrote:
The surge protection of a PC PSU (or even an external "surge strip") isn't going to protect you from a lightning strike.

I somewhat doubt that, but I'm not saying it's impossible either. Care to explain why a surge protector combined with a decent psu won't protect from a strike? I thought that was the whole purpose of computer power strips. I've never experienced a blowout from lightning, so perhaps that makes me biased to the lightning argument.
just brew it! wrote:
What's the best backup method for bringing your system back from the dead if you experience a drive failure? Whole drive backups/restoring take forever, and I'd like to know if there is a speedier way of doing them other than raid1.

Preservation (or quick restoration) of functionality following a single drive failure is *exactly* what RAID is about. So either use RAID-1, or just deal with the time required to restore from a backup image. You can speed up the restoration process by using an eSATA or USB3 backup drive instead of USB2.
I could do eSATA, but my board or external drive doesn't support USB3.
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 9:31 am

bdwilcox wrote:
This is a little off-topic, but RAID definitely hinders data recovery. If you have no backup and your hard drive fails, there's a good chance you can recover some or all of the data on that drive, expensive as such an exercise might be. Adding a RAID array to that calculation makes the odds of recovery much lower and the cost much higher.

For RAID-1 and RAID-5, if a *single* drive fails you don't *need* data recovery, since you can just copy the files off normally.

For a RAID-1 with two failed drives, it shouldn't be much more difficult/expensive than for a normal (single) drive, since RAID-1 just mirrors the data.

For a RAID-5 with two failed drives, yeah you're probably screwed.

Your point is probably more applicable to data recovery efforts following data loss caused by user error or malware...
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 9:42 am

l33t-g4m3r wrote:
just brew it! wrote:
The surge protection of a PC PSU (or even an external "surge strip") isn't going to protect you from a lightning strike.

I somewhat doubt that, but I'm not saying it's impossible either. Care to explain why a surge protector combined with a decent psu won't protect from a strike? I thought that was the whole purpose of computer power strips. I've never experienced a blowout from lightning, so perhaps that makes me biased to the lightning argument.

The surge from a lightning strike is orders of magnitude beyond what a consumer surge suppressor or PSU can handle.

Some of the damaging surges don't even come in via the power cord. The EM field of a lightning strike can induce powerful currents in any external cables coming out of the box -- keyboard/mouse cords, VGA/DVI cable, Ethernet cable, etc. -- and the surge will get into the system that way even if the AC line is protected.

A co-worker's father's house took a lightning hit a while back. Pretty much *all* of his electronics -- even stuff that wasn't turned on at the time -- was destroyed.
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 9:47 am

OT: my house was saved from a lightning strike by our mailbox of all things. The 'box had a whole corner blown off, and all that happened to the house was one breaker tripping.

The new mailbox doesn't have chicken wire reinforcing a layer of mortar, so that trick won't work again.
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 9:57 am

mikeymike wrote:
Backup systems take many forms because a backup system can perform some functions and not necessarily others. If someone wants a backup system, I ask the question: Are you looking for protection against, for example, a hardware failure, and/or are you looking for protection against accidental edits/deletions?

A RAID1 setup that covers some data that you wouldn't like to lose is a good thing. It is a backup system to protect against the possibility of a sudden hard disk failure. As someone rightly pointed out on another thread, it doesn't protect against data corruption (like say Word mangling a precious document).

However, if you're looking for protection against accidental edits/deletions or file corruption, you should look elsewhere. You might want to have RAID1 and another backup system alongside it, it depends how much you want to protect yourself from potential risks and possibly how much you want to spend.

RAID is like having "backup hardware", but this is not the same as a "data backup". When people talking about "backing up" their computer, they are talking about data backup.

RAID is not data backup and for clarity's sake it should not be referred to with the term "backup" at all. Please, since we have two different terms, lets use them! RAID is hardware "redundancy", and in fact, the "r" in RAID stands for "redundant". It's not "BAID". RAID is not about keeping your data safe, it is about keeping your machine running in the event of a disk failure. Backups are for keeping your data safe.

RAID is not backup. Every person with computer system administration training knows this. You will never hear someone with computer system administration training refer to RAID as a "backup". You'll never hear someone say "restore a file from yesterday's RAID for me". RAID is not backup at all, and there is no ambiguity about the separation of those terms.
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 10:04 am

I'll have to ask our sysadmin to restore something from yesterday's RAID now. :D
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 10:09 am

just brew it! wrote:
bdwilcox wrote:
This is a little off-topic, but RAID definitely hinders data recovery. If you have no backup and your hard drive fails, there's a good chance you can recover some or all of the data on that drive, expensive as such an exercise might be. Adding a RAID array to that calculation makes the odds of recovery much lower and the cost much higher.

For RAID-1 and RAID-5, if a *single* drive fails you don't *need* data recovery, since you can just copy the files off normally.

For a RAID-1 with two failed drives, it shouldn't be much more difficult/expensive than for a normal (single) drive, since RAID-1 just mirrors the data.

For a RAID-5 with two failed drives, yeah you're probably screwed.

Your point is probably more applicable to data recovery efforts following data loss caused by user error or malware...

It depends on the RAID type but data recovery is much more difficult with RAID which is why most data recovery places charge double or more for RAID data sets including RAID 1. The difficulties depend on the RAID type: mirror or parity. For example, RAID 1 failures I've seen have been mirror corruption (usually from a failing controller), corrupted data copied from one drive to the next (a mess if the corruption hits the MFT) and broken mirrors that refuse to mount and you don't know which drive is the failing one. As for RAID 5, I've had second drives fail during a rebuild; this is why we now use RAID 6 since many of our arrays can take more than a day to rebuild they're so huge nowadays.
 
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 10:17 am

derFunkenstein wrote:
I prefer RAID5 to RAID10, if only because it's more flexible in setup. RAID10 is going to require drives in multiples of 4 (I think; it might be exponential. I've never investigated more than 4 drives for RAID10 before) RAID5 can take any number of drives from 3 to ∞+1.


RAID 10/0+1 only require 2n drives, n > 1 (any even number 4 or larger). Just remember that it's a mirrored set of stripped drives (or a stripping of mirrored drives), and it'll make sense. I agree that RAID 5 is more flexible in setup, but RAID 5 is a guaranteed failure after 2 drives die. Conversely, a RAID 10 setup *can* die after only 2 drive failures, but has the possibility of surviving all the way up to half the drives dying, depending on which drives are the ones that fail.
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Re: People who say "RAID1 is not a backup"

Thu Apr 14, 2011 10:27 am

bthylafh wrote:
I'll have to ask our sysadmin to restore something from yesterday's RAID now. :D


Having a backup of a RAID set is still just that a BACKUP!. The whole concept is that backups are stored on separate systems, hardware or whatever. RAID, as has been stated, is use to for system resiliency. i.e. maintaining system uptime, should there be a minor hardware failure. Backups are made to prevent complete data lose in the event of a catastrophic failure. RAID in and of itself doesn't not automatically backup data. In other words RAID allows for hardware failure in a system, backups allow for entire system failure. There is a difference.

Backups can consist of separate disk arrays making redundant copies of raid sets, often called near line or inline storage, as disk is faster than tape. However it is still a backup. I manage two SAN's the second used as a DR site making redundant copies of our SAN volumes (which are raid sets). It is just a different form of backup strategy.

At the end of the day RAID != Backup no matter what the form.
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