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Re: Flexraid Calculator

Blanker-2
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Flexraid Calculator

I am trying to understand the usable space with the flexraid format amongst disks of different capacities.  The online calculator is missing certain disks like 5TB and 650TB, etc.  Any documentation I may have missed?

 

It seems as though the flexraid format needs to have disks of the same size.  So a flexraid (RAID5) array of two 2TB diks and two 5TB disks will yeild a usable volume of  6TB (esentially wasting 3TB of each 5TB disk, and reserving one 2TB disk for redundancy)?

Model: EDA500|ReadyNAS Expansion Chassis 5-Bay
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StephenB
Guru

Re: Flexraid Calculator


@Blanker-2 wrote:

Any documentation I may have missed?

 




The software manual ( http://www.downloads.netgear.com/files/GDC/READYNAS-100/READYNAS_OS_6_SM_EN.pdf ) does talk about FlexRaid expansion - see pages 35-36.

 


@Blanker-2 wrote:

It seems as though the flexraid format needs to have disks of the same size.  So a flexraid (RAID5) array of two 2TB diks and two 5TB disks will yeild a usable volume of  6TB (esentially wasting 3TB of each 5TB disk, and reserving one 2TB disk for redundancy)?


That is what the manual says.  One small correction - the parity blocks that create redundancy are evenly spread across all the disks.  But that change your capacity assessment.  Anyway, you understand the underlying principle, so you can compute capacity w/o the calculator.

 

There could be some special cases where unequal disks can be used - I think @jak0lantash posted the results of a lot of expansion experiments he did some months ago.

 

With that particular combination of disks, you get 7 TB  by creating a 2x2TB RAID-1 volume and a 2x5TB RAID-1 volume.  X-RAID of course gives you 9 TB. The rule for X-RAID single redundancy is "sum the disks and subtract the largest".

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StephenB
Guru

Re: Flexraid Calculator


@Blanker-2 wrote:

Any documentation I may have missed?

 




The software manual ( http://www.downloads.netgear.com/files/GDC/READYNAS-100/READYNAS_OS_6_SM_EN.pdf ) does talk about FlexRaid expansion - see pages 35-36.

 


@Blanker-2 wrote:

It seems as though the flexraid format needs to have disks of the same size.  So a flexraid (RAID5) array of two 2TB diks and two 5TB disks will yeild a usable volume of  6TB (esentially wasting 3TB of each 5TB disk, and reserving one 2TB disk for redundancy)?


That is what the manual says.  One small correction - the parity blocks that create redundancy are evenly spread across all the disks.  But that change your capacity assessment.  Anyway, you understand the underlying principle, so you can compute capacity w/o the calculator.

 

There could be some special cases where unequal disks can be used - I think @jak0lantash posted the results of a lot of expansion experiments he did some months ago.

 

With that particular combination of disks, you get 7 TB  by creating a 2x2TB RAID-1 volume and a 2x5TB RAID-1 volume.  X-RAID of course gives you 9 TB. The rule for X-RAID single redundancy is "sum the disks and subtract the largest".

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