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April 5th, 2018 22:00


Hello Dell And others,


Good Day.


I know this is a low brainer but I appreciate any feedback.

This is about Raid Array having hot spares.

1. Raid 1 (Mirroring)

Does raid 1 need hot spare to perform fault tolerance?


2. Raid 10 (Stripe and Mirror)

For Example, I have 4 SAS Drives configured in Raid 10, Does This one also need a hot spare to perform HA?


3. Raid 5 (Striping)

I Have 3 HDD (600 GB Each) configured in Raid 5 with a logical volume capacity around 1.2 TB.

Do I need to have a hot spare for this one in order for the parity to perform HA?


I Hope you can help me with my confusions.


Thanks a lot!





4 Operator


1.8K Posts

April 10th, 2018 09:00

All the raid configurations you mention are fault tolerant, they can lose 1 drive, raid 10 possibly more, without a hotspare. Hot spares just add to the safety of arrays, they will become an full functioning active member of an array should a drive fail. Hotspares have nothing to do in creating or maintaining parity, no array must have a hotspare (at least not in the general consumer class of raids). Personally I institute a hotspare for most of my client's arrays, takes the pressure off me to replace a failed drive, adds a margin of safety.

"And somebody stated that for R5 you need to have hot spare in order for the array to have Fault Tolerance."

That "somebody" need some basic raid knowledge, Raid 5 does not need a hotspare to have fault tolerance, it can lose 1 disk, then it runs in degraded mode until the faulting/dead disk is replaced and the rebuild process completes. 


274.2K Posts

April 6th, 2018 06:00


Hopefully I can clarify this for you. Fault Tolerance and High Availability (HA) are based on Virtual Machine redundancy, and not on the hosts Virtual Disk Raid Configuration.  Now it is recommended to have Hotspares to increase failure redundancy, but it isn't a basis in Esxi Fault Tolerance or HA. You can find more here for a detailed explanation of Fault Tolerance and HA, I know these guides are from an older version of ESXi, but it has a good explanation of both.

Let me know if this helps. 

April 9th, 2018 18:00

Hello SIr Chris,

Thanks for paying attention to my query.

I'm not talking about any hypervisor here though.

I've attended a storage training just recently.

And somebody stated that for R5 you need to have hot spare in order for the array to have Fault Tolerance.

So Now I'mconfused.


How bout for R1? It only requires 2 HDD.

What if I dont have hot spares? Will the array still be there in case of 1 HDD failure?


Please advise.

Thanks a lot :D



April 10th, 2018 17:00


very informative.


I think all is clear now.


Thanks a lot man!

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