doubt about the size of Raid5

[rasalghoul74]

hello everyone I have a doubt / problem, I have a 431p with 4 4tb disks configured in raid5 (3 + 1), having run out of space I bought a 453D with 4 6tb disks, I have configured everything updated the firmware and in the end I have tried to create the new raid5, it reads me the 4 disks with usable space each of about 5.75tb, I select 3 and it creates a raid with only 10.89tb (i.e. exactly the same size as the other nas with disks from 4tb), am I wrong something? is there a size limit? i searched on the internet but maybe i'm wrong the search terms, i hope you can help me

[Moogle Stiltzkin]

https://www.servethehome.com/raid-calculator/


when you create a raid5 thick, by default only 50% is set to usable space. For the rest of the 50%, you have to change the allocation from 50% to 100% for the FULL usable space.

But normally people just change the allocation by little increments to as much as they currently require. And allot more over time when they more space. It wasn't advised to allocate 100% right away unless you need to (forgot the reason why).

So i'm wondering is that your issue? you did not know about the default 50% allocation when you first create the raid5 thick volume?

[rasalghoul74]

this is my situation, where i can choose to use all the space?

[Mousetick]

You need to select all 4 disks. The total capacity of the RAID 5 will then be 3 times that of 1 disk.

[rasalghoul74]

if i select all 4 disk i have a total of 16tb +/- and no security disk, i have the same situation as i wrote with a 431p but with 4 disk of 4tb each

[rasalghoul74]

looks like if there is a limit, the capacity of 4 hard disk by 4tb is the same of 4 disks of 6tb, when i create a raid 5 with 4 disk by 4tb( 3 disk + 1 security disk) i have 10tb of free space the same with 6tb disks

[Mousetick]

I'm not sure what you mean by security disk, I guess you mean spare disk?

RAID 5 with 3 x 4 TB disks + 1 x 4 TB spare disk = 8 TB (7.27 TiB) capacity
RAID 5 with 4 x 4 TB disks = 12 TB (10.9 TiB) capacity

RAID 5 with 3 x 6 TB disks + 1 x 6 TB spare disk = 12 TB (10.9 TiB) capacity
RAID 5 with 4 x 6 TB disks = 18 TB (16.37 TiB) capacity

As far as I know for your model the 16 TiB limit applies to the capacity of an individual volume, not to the capacity of the storage pool or RAID.
What was the estimated RAID capacity displayed in the volume creation "wizard" (lower right corner of the disks list) when you selected all 4 disks?
Or did you add the 4th disk after the RAID 5 was created?

[rasalghoul74]

)yes, pare disk, excuse me, i'm italian
the wizard show me exactly example that you report (RAID 5 with 3 x 6 TB disks + 1 x 6 TB spare disk = 12 TB (10.9 TiB) capacity or RAID 5 with 4 x 6 TB disks = 18 TB (16.37 TB capacity)
my question is: why 3x6tb+1 6tb that show wizard give me only 10.9tb and not 18tb+1 6 spare ?

[dolbyman]

You should exchange those SMR drives ..bad purchase

16TB limit is only with CAT1 devices ..a 431p is a storage pool capable CAT2 and is not limited to on pools or static volumes

[rasalghoul74]

no sorry in this case i was speaking of a ts-453D ( i have also a 431)

[dolbyman]

same goes for that

[rasalghoul74]

than my problem is in wd red and not in qnap, right?

[dolbyman]

they will become your problem when they go super slow and kick out of your raid

but that has nothing to do with capacity expansion

[rasalghoul74]

in 431 i have same wd red by 3 year and no problem (for now)
but have you any solution now for my capacity problem?

[dolbyman]

wd introduced the smr disaster recently so your 3 year old disks probably do not use smr (google it)

post and english screenshot of your volume manager and the capacity expansion dialoge