Disk pool number of disks can survive

[Saif]

Hi guys, I am new to netapp and I want to know the maximum number of disks failure would still make disk pool running if I have this model

E2860 System Shelf

with 180 disks 14TB in each

I have created one pool for the whole 180 x14TB

I know that 6 disks work as hotspare.

[AlainTansi]

That is correct, 

For a Disk Pool Drive Count from 128-191, the default number of Drives Reserved for Preservation Capacity should be 6.

https://kb.netapp.com/Advice_and_Troubleshooting/Data_Infrastructure_Management/E-Series_SANtricity_Management_Software/How_many_drives_should_be_assi...

Please if this post resolved your issue, please help others by selecting ACCEPT AS SOLUTION or adding a KUDO or both!

[Saif]

So does that mean if I lost those 6 disks I should immediately replace disks before one more disk fails or I will lose my data

And what about RAID 6 as default RAID for the disk pool?

[AlainTansi · Accepted solution]

So by default, Disk Pool uses RAID level 6. And for RAID level 6 you should have the tolerance of 2 drive failure before any subsequent data lose.

What the 6 Preservation Capacity Drives means is that, slices of free block are reserved on each disk in the pool that sums up to a total equal to 6 disk drives capacity. These are not any 6 physical disks that you can identify them individually.

You can understand more on this by visiting

NetApp Hardware universe https://hwu.netapp.com/Controller/Index?platformTypeId=2357027#none

How do Volume Groups differ from Dynamic Disk Pools in E-Series storage? https://kb.netapp.com/Advice_and_Troubleshooting/Data_Storage_Systems/E-Series_Storage_Array/How_do_Volume_Groups_differ_from_Dynamic_Disk_Pools_in_E-...

RAID Levels and Data Redundancy on page 20 https://library.netapp.com/ecm/ecm_download_file/ECMP1189231

[Saif]

so that's mean I have the following before I lose data in disk pool RIAD 6 -(2) disks reserved capacity 6 disks total of 8 disks Thanks a lot for the clarification

[AlainTansi]

I am glad that my explanation was accepted and gave you some clarifications. However,  i am not clear if you understood 8 to be a number of physical disks that you have available. So just to further clarify

- 2 is the tolerated number of disk that can fail in the pool and there will be no concern of data lose.

- 6 is the number of free capacity that is used by storage pool for  background operation which you can not take control of. 

6 x 14TB = 84TB

84/180 ~= 466GB

(ie there is approx 466GB of free space reserved on each of the 180 disks)