All about RAID is not BACKUP, general discussion

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All about RAID is not BACKUP, general discussion

Joseb

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If you consider yourself a newbie and is after a NAS, you probably want to go for Synology. My experience is that their software is easier to understand and work with.
And remember, RAID is not the same as backup.
Hi Orbit
What do you mean that 'RAID is not a backup'? You are going to confuse him by saying that. Please explain what you mean by that to him. You are assuming he has your frame of reference.
 

jeyare

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To be sure:
RAID isn’t backup, because RAID is kind of redundancy for your data in disk group attached in single device (e.g. RAID in NAS, or computer) = it’s a combination of multiple (more than 1) disk drives into single disk group with defined behavior/purpose and clearly disk failure tolerance. For an example - With RAID you can get better speed than single disk operation. Or you can get heavy disk failure tolerance for an archiving purposes. There is such large list of purposes.

RAID NEVER protect your data from accidental user mistakes (data deletion, data overwrite, disk format, ...).

RAID never protect you from defined disk failures in the disk group (up to chosen RAID model).

RAID never protect you from security issues (malware, ransomware, stolen disk drive, fire,...).

For such data protection (single or multiple copy of your data for a restore purposes in case of the accident) we have process called Backup.

Then RAID isn’t Backup.
 

Joseb

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To be sure:
RAID isn’t backup, because RAID is kind of redundancy for your data in disk group attached in single device (e.g. RAID in NAS, or computer) = it’s a combination of multiple (more than 1) disk drives into single disk group with defined behavior/purpose and clearly disk failure tolerance. For an example - With RAID you can get better speed than single disk operation. Or you can get heavy disk failure tolerance for an archiving purposes. There is such large list of purposes.

RAID NEVER protect your data from accidental user mistakes (data deletion, data overwrite, disk format, ...).

RAID never protect you from defined disk failures in the disk group (up to chosen RAID model).

RAID never protect you from security issues (malware, ransomware, stolen disk drive, fire,...).

For such data protection (single or multiple copy of your data for a restore purposes in case of the accident) we have process called Backup.

Then RAID isn’t Backup.
Jeyare, I am curious. Don't all those NEVERs also apply to any type of backup and or external disk.? I am not getting why it's not a backup. If he had 3 other copies of his data on three external drives will his RAID setup serve as a backup? I think I am missing a fine point here.
 

jeyare

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this thread has been created from multiple posts, related to this general RAID topic
Reason: maintained/clean thread primary topics
 

jeyare

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back to @Joseb consideration re RAID:
Don't all those NEVERs also apply to any type of backup and or external disk.? I am not getting why it's not a backup. If he had 3 other copies of his data on three external drives will his RAID setup serve as a backup? I think I am missing a fine point here."

Scenarion n.1:
two HDDs in RAID1 in NAS
file: picture.psd created last week, backup to another NAS performed
edited today in computer connected to NAS (computer doesn't have UPS connected)
SAVE operation in the computer (no automatic save feature is in usage)
there is a power outage, which caused that file has been written incomplete = bad block discovered = no physical HDD damage observed, just sw based damage

What you will see in both disk (RAID1) in standard file system = two same written blocks, include the bad block
You have damaged file in both mirrored disks.

You have choice to use your previous backup to restore last saved (backuped) file.
When you have 3-2-1 backup adopted to your environment, then you have lot of chances for the file restore.

OFC:
-there is heavy list of possible situation covering, But for the "RAID isn't backup" purpose description is this one useful.
 

jeyare

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same you can imagine for the deleted file from your primary NAS. Your data is lost in the RAID.
OFC, you have special choice for a data restoration till you wipe-out the HDD/SSD. But I will use just simple description for an understanding.
 

jeyare

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OFC you can argue that you have backup NAS also with RAID. Yes.
What must happen to accidentally delete the same file in 3 different backup site/locations/devices (NAS, external disk)? OFC = wrong backup plan.
 

jeyare

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when your primary NAS is encrypted by RANSOMWARE attack, there is no RAID that will help you. Just backup.
 
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Last edited:
Would it help to frame the discussion in terms of "risks" and "mitigations".

Risks would include...
- Fire, Water, Natural Disaster
- Theft or Physical Tampering
- Virus, Malware, Ransomware
- Accidental Corruption or Deletion (Human Error)
- NAS Hardware Failure
- HDD/SSD Failure

Mitigations would include...
- RAID With Redundancy
- A Copy on a Different Set of Storage Media (Same Location)
- A Copy on a Different Set of Storage Media (Offsite Location)
- A Copy on a Cloud Service

Then it is possible to evaluate the best mitigation(s) and associated cost against each risk, understand where mitigations overlap, weigh the time/cost that would be required to restore normal operations, etc.

For example, the risk from Fire, Water, Natural Disaster cannot be mitigated by RAID or a Same Location copy; but could be mitigated by an Offsite Location copy or a Cloud Service. If you are in an area where volcanic activity, earthquakes, or tsunamis are a risk, then consider where the Offsite or Cloud is physically located.

Ron
 

jeyare

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then follow all mentioned posts:

1. for home users with primary operation model & more than 2 bay NASes in usage:
- media library (photos, movies, home videos,...)
- basic document storage
- AB4B for few computers
what is major market target of Synology (up to 5 bay NASes)

A. is better to use RAID1/5/SHR with adequate backup policy
B. RAID6 (SHR2) for such usage is a waste of every bay occupied with such redundancy model
because it is a mislead understanding, that RAID6 will be a backup for your data. Till first ransomware attack or data accidental deletion, or bad block.

2. for home users, but with specialized operation (photographers only, youtubers, engineers, self-employed sw freelancers, ...)
is better to use different RAID setup for different data =multiple RAIDs in single NAS.
Few examples:
- for photo catalog RAID0 with SSD - when speed is more important feature than redundancy and copy of the catalog is based on 3-2-1 backup policy (then no fear about a data lose). To be sure Photo catalog is't same as Photo archive. Photo catalog is for an editing purpose.
- docker operation or Drive - when speed and redundancy is important and total data you can count in tenths GB - RAID1 is enough and faster than RAID5 (write I/O and rebuild time)
- when frequently grow up of the data is expected, then RAID5 (or SHR) for 3+ disk in the group is really good choice. Then spending of 20 minutes with excel can help you better calculate of your data storage needs = save a money from absurd setup of RAID with 10+ TB (without an adequate utilization) and then spend more than 24hours of rebuild time is horrible = base of frequent claims "why is my NAS so slow".
What about split of all stored data to:
a) old data in archive
b) and frequently used data (or newest only) in the adequate RAID mentioned?

Same principle is valid for the backups:
- is better to run small batch (specially to cloud based targets), than big bunch of TB with really low performed LAN or internet connection (upload, also download for a restore). Because waiting x-days for the backup is tricky, even week and more.

People like purchase costly smartphones or computers, then frequently save money for the data storage/backup. You can purchase new phone when old will die, but lost data you can't bring back to life.

PS:
pro-grade persons can read many reviews how FS performance can be affected by specific RAID usage.
 

jeyare

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you can also read (all posts), how is RAID complicated in operation and how you can handle some RAID errors and how you can't. Then the backup is your friend.
 
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This is really easy. If your NAS catches fire, RAID will not help you get your data back.
 
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Can't believe we need a thread here when Bro' Google has such an immensity of resources on this common-sense topic.

My great-aunt would say... "don't put your eggs all in one basket". Seems applicable here.
 

Joseb

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Can't believe we need a thread here when Bro' Google has such an immensity of resources on this common-sense topic.

My great-aunt would say... "don't put your eggs all in one basket". Seems applicable here.
My guess is that NAS gurus are using the term 'back up' in a certain way. My guess is that they mean that it is not a backup if its the only place where your data exists. Which is really what they should be saying. For those of us new to NASs the term "RAID is not a backup" sounds non-nonsensical. It's like saying a car is not transportation. To the person new to NASs their data was put somewhere and is therefore a backup. They are not even thinking in terms of if it also exists somewhere else. I recommend that instead of just spitting out "Raid is not a back" to new people, that time is taken to explain what that sentence means. I could be wrong but I have figured out it means that if the only place you have your data on a Raid implemented NAS then the fact that it's RAID does not help you in a catastrophe. But the same thing is true of having multiple copies of the same data in one place. So I don't see why mentioning that's a Rad is not a backup. Where does that get you? What follows from that? Maybe I am missing something.

And what's the purpose of a forum if one cannot ask a question? That Google exist doesn't add to the discussion. It on the other hand sound a lot like my linux friends who like to self righteously say RTFM. Which I have never seen as a civilized response to any question.
 

fredbert

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One thing we have here, vs other forums, is a Resources section. I've often seen replies to basic questions that state "this has been covered lots already, use the search". This may be true but even for a generally savvy person it's not always easy to formulate the right search terms, plus some places then add captcha for each search and a search limit per X minutes (unless you register, and who knows if that forum us the right place anyway).

With the Resources (or Blog) section we can add articles that cover a specific topic in more detail, or a link to a place that does the same. Then when an oft posted question happens the reply can be to point to the detailed answered.
 

jeyare

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yeah @Joseb don't worry about your attitude to ask, when you don't understand.

Sometimes we mix milk with beer from someone perspective. Of course, but this forum is a really great place to discover new galaxies in our daily lives.

As I have written many times, only stupid people do not ask before they go wrong. I've been stupid many times :cool:
now I'm older.
 
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Definition:
In information technology, a backup, or data backup is a copy of computer data taken and stored elsewhere so that it may be used to restore the original after a data loss event.
Source

Ergo, RAID is not backup.

Further...
While RAID may protect against physical drive failure, the data is still exposed to operator, software, hardware, and virus destruction. Many studies cite operator fault as a common source of malfunction,[75][76] such as a server operator replacing the incorrect drive in a faulty RAID, and disabling the system (even temporarily) in the process.[77]
An array can be overwhelmed by catastrophic failure that exceeds its recovery capacity and the entire array is at risk of physical damage by fire, natural disaster, and human forces, however backups can be stored off site. An array is also vulnerable to controller failure because it is not always possible to migrate it to a new, different controller without data loss.[78]

Source
 

jeyare

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RAID-isnt-Backup.png
 

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