is there an unraid equivalent of synology SH2?


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I'm trying to decide whether to go for FreeNAS self build, unraid self build or buy a synology. I have a lot of randomly sized hard drives. My data is very important to me, so I want at least 2 parity drives. I found a calculator for Synology, which tells me it'll give me 18.5tb of space with 2 parity drives under RAID array type "SH2". It also shows standard RAID 6 (with 2 parity drives) would only provide 4.5TB of space. Is there any similar raid type to SH2 with unraid?

 

My spare hard drives (in TB): 2, 2, 3, 3, 2, 4, 0.5, 6, 2, 6, 1

 

Synology SH2 & RAID space calculator for random hard drive sizes:
https://www.synology.com/en-uk/support/RAID_calculator?hdds=2 TB|2 TB|3 TB|3 TB|2 TB|6 TB|2 TB|6 TB|500 GB|1 TB|4 TB

 

Also, is there a similar calculator for UNRAID with its supported raid types? The only one I could find was an old out-dated unraid calculator that was made in 2009 (!) by an unraid user and doesn't allow you to select the number of parity drives or raid type like the synology calculator.

Old unraid calculator from 2009, probably out of date: http://unraid.category5.tv/

 

Would appreciate thoughts on this.

 

Thanks in advance

Edited by Bob2
add link to what I'm referring to.
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Posted (edited)
3 hours ago, trurl said:

The 2x6TB disks would be parity and the total of all the others would be your total data capacity. 

thanks. It sounds like a similar capacity to SH2 which is good.

 

Is there support to prevent silent bitrot such as bad sectors? etc. like in synology where it scans regularly using BTRFS scrubbing?

 

Will it email me when it detects a problem or it's time to change a drive?

Edited by Bob2
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5 hours ago, Squid said:

When Unraid detects a read error in the array, it will recalculate the data that should have been present and re-write it. 

... so that means it CAN correct bad sectors but doesn't mean it regularly WILL correct bad sectors. 

 

Will it do anything regularly to detect & repair bad sectors or incorrect data? Like how synology does.

 

Thanks

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1 minute ago, Bob2 said:

Will it do anything regularly to detect & repair bad sectors or incorrect data?

Most people schedule parity checks once a month, a parity check reads every bit of every drive in the parity array and confirms the parity calculation.

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Posted (edited)
4 minutes ago, jonathanm said:

Most people schedule parity checks once a month, a parity check reads every bit of every drive in the parity array and confirms the parity calculation.

Thanks so much. In that case it's looking like unRAID is probably the best option! Is it easy to schedule parity checks or does it require installing some extra plugin?

 

I have had some HDDs in the past return faulty data without there actually being a read error / bad sector (such as files being corrupt over time etc.). I'm guessing unRAID cannot protect against this?

Edited by Bob2
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Just now, Bob2 said:

Thanks so much. In that case it's looking like unRAID is probably the best option! Is it easy to schedule parity checks or does it require installing some extra plugin?

It's been too long since I spun up a box stock version, but I think the monthly schedule is there by default, in any case it's easy to do. There is a plugin to handle more complex scheduling, like pausing the check and resuming at specific times to minimize impact, or other triggers.

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3 minutes ago, jonathanm said:

It's been too long since I spun up a box stock version, but I think the monthly schedule is there by default, in any case it's easy to do. There is a plugin to handle more complex scheduling, like pausing the check and resuming at specific times to minimize impact, or other triggers.

That's good.

 

Can unRAID detect & correct silent corruption (e.g. where a file goes bad over time and returns a different MD5 hash)? I'm not actually sure any RAID setup can do this at present.

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3 minutes ago, Bob2 said:

Can unRAID detect & correct silent corruption (e.g. where a file goes bad over time and returns a different MD5 hash)?

It can detect corruption if you btrfs, but it can't correct it since each data device is an individual filesystem without redundancy.

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23 hours ago, JorgeB said:

It can detect corruption if you btrfs, but it can't correct it since each data device is an individual filesystem without redundancy.

ouch. So I guess that's a pretty major flaw and something that the Synology does do. I'll have to re-consider my options. Perhaps I'll look at offline backups that aren't at risk of viruses or other wares.

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3 hours ago, Bob2 said:

So I guess that's a pretty major flaw

In the 10+ years of using Unraid, I have never experienced a case of bitrot (I am using the Dynamix File Integrity plugin to monitor this).

 

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