Synology Box RAID configuration

FrantzM

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Apr 20, 2010
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According to Raid-failure.com the probability of a successful rebuild after 1 drive in a 5 drive array fails is 99.8%. "Highly probable" is way overstated.

dminches

The success probability of the rebuild process and the probability of more than one drive failing are two different things. One (1) disk fails in a RAID 5, true, it is 99.8% probable that the array can be rebuilt while never losing the use of your data. That is one of the thing RAID 5: it allows continuity of operation in the event of ONE (1) disk failure .. if 2 drives were to fail in RAID 5 (emphasis on 5) simultaneously or in an unfortunate sequence: Let's see the scenario:
You have ONE disk failure and promptly exchange the disk with a new in disk, your array is rebuilding.. you are happy. I is however a slow process. can take several days for a 12 TB array. You must pray that nothing happens to any one of the other disks during the rebuilding else you lose all your data. If two disks were to fail simultaneously in operation, you lose all data too.
In most cases people use the same drives to build a RAID 5 array increasing thus the probability of 2 drives going out at the same time. Interestingly SHR allows us to build a RAID-like array with dissimilar drives in some ways mitigating the risks of two drives going at the same time or in close sequence..

RAID 5 is protection and insurance for operation continuity RAID 5 doesn't replace Back-up... it is a serious difference.
 

ddk

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May 18, 2013
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According to Raid-failure.com the probability of a successful rebuild after 1 drive in a 5 drive array fails is 99.8%. "Highly probable" is way overstated.

That 0.2% caught up with me 3 or 4 times already :(:(! Learnt my lesson after the first raid disaster...

david
 

FrantzM

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That 0.2% caught up with me 3 or 4 times already :(:(! Learnt my lesson after the first raid disaster...

david

I agree with your point though better safe than sorry : BACK-UP... and just have a non-spinning disk somewhere backing yup your back-up or better Coud Storage.

OTOH I have had to rebuild dozens of RAID 5 arrays in my line of work.. usually works.. Out of perhaps 30 , i have had 2 failures and those were because , perhaps, we weren't patient enough .. Putting the arrays back in full operation while ongoing re-building.
 

ddk

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There are other causes too that raids aren't immune to Frantz, right now I'm unsuccessfully dealing with a corrupted directory and a 5 disc raid, haven't found any software to fix the directory. Any suggestions?

david
 

dminches

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Oct 22, 2011
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Believe High Fidelity

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That 0.2% caught up with me 3 or 4 times already :(:(! Learnt my lesson after the first raid disaster...

david

Lol. Yes I have had it happen twice to me for my movie servers and I had to re-rip them all over again.

Real world results and an algorithm on a website are two different things.
 

Believe High Fidelity

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I certainly don't and would be happy to read the statistics that backed your comment.

First stop Amazon.com

Check 1,2,3 star reviews on new purchases. Once you factor in 2-3yrs+ no covered under the reviews the % goes up

You will see just how often they die or die together (2+ in the same day or time period).

Or you can take your fellow audio guys words who have experienced it first hand several times.
 

Believe High Fidelity

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There are other causes too that raids aren't immune to Frantz, right now I'm unsuccessfully dealing with a corrupted directory and a 5 disc raid, haven't found any software to fix the directory. Any suggestions?

david

Any you wont find any that a regular Joe can use. This is another point as to why I dont use RAID anymore even with enterprise grade drives that have features for preventing corruption in data

Here is a very entertaining and informative video on what you can expect trying to recover the data yourself, but you will have to hire someone to do it (and it is very $$$)

All of our data is GONE!
 

dminches

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Oct 22, 2011
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First stop Amazon.com

Check 1,2,3 star reviews on new purchases. Once you factor in 2-3yrs+ no covered under the reviews the % goes up

You will see just how often they die or die together (2+ in the same day or time period).

Or you can take your fellow audio guys words who have experienced it first hand several times.

I know hard drives fail. I have experienced them many times. However, during the 10+ year period that I have had 2 or more raid boxes running I have never experienced 2 hard drives fail at once or a 2nd one fail during the rebuild after the first one did. I am sure it has happened but the chance of it is not likely.
 

edorr

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May 10, 2010
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In my view, you don't need immediate failover capability. So RAIS is nice to have but not necessary. A lightning strike can take out your entire RAID array. Most important thing is to back up periodically to an offline additional (USB) drive.
 

dminches

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Oct 22, 2011
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RAID 5 is protection and insurance for operation continuity RAID 5 doesn't replace Back-up... it is a serious difference.

I completely agree which is why I have both.

While I don't think that the chance of losing all your data in a raid array is 0.2%, the point of my comment referring to the statistics was to disagree with the poster who said the chance of total failure was "highly probable."
 

Believe High Fidelity

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I know hard drives fail. I have experienced them many times. However, during the 10+ year period that I have had 2 or more raid boxes running I have never experienced 2 hard drives fail at once or a 2nd one fail during the rebuild after the first one did. I am sure it has happened but the chance of it is not likely.

Same here. I didnt have a lot of data at the time on these movies servers so I hadn't backed them up yet and I had never experienced raid failure ever.

Point is probability low or even a fraction of a % you could end up a statistic and buying one more drive for a Raid 6 to me is worth the investment compared to the loss of data and/or price to get it recovered.

So if you RAID you MUST have a backup in place, but as aforementioned I do see any value in using RAID anymore. Little advantage for what you get in return
 

microstrip

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May 30, 2010
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An aside from a non expert ...

Most of the recipes and suggestions usually presented about data storing and backup address people who have large amounts of data of permanently changing - not the typical audiophile with a few thousands of recordings with a stable content that is just being slowly increased.

Considering my small size needs in the forthcoming years and the price of media I decided for a Raid1 system using 4T disks and I am considering two separate back up units. Any thoughts on this strategy?
 

Believe High Fidelity

[Industry Expert]
Nov 19, 2015
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ibelieveinhifi.com
An aside from a non expert ...

Most of the recipes and suggestions usually presented about data storing and backup address people who have large amounts of data of permanently changing - not the typical audiophile with a few thousands of recordings with a stable content that is just being slowly increased.

Considering my small size needs in the forthcoming years and the price of media I decided for a Raid1 system using 4T disks and I am considering two separate back up units. Any thoughts on this strategy?

Since a RAID1 is already a copy of each drive adding a single external USB HDD of the same capacity size would be fine for a 3rd copy of your music. Plus it is nice to have for travel you can plug it into a USB dac at your friends for auditioning
 

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