andvm
Hot Shot
Hot Shot

RAID type in vSAN Default Storage Policy

Jump to solution

Hi,

Why Hard disk 1 is 2x RAID 0 and Hard Disk 2 and remaining components are RAID 1 ? (Using default vSAN policy FTT=1)

Wouldn't 2x RAID 0 make a RAID 1 so why listed differently?

andvm_0-1648629768007.png

Thanks

0 Kudos
1 Solution

Accepted Solutions
Tibmeister
Expert
Expert

So in the case of the disk that's > 255GB, it's getting striped into two objects of equal size, which is a single RAID0 object.  Those two components comprise the single object that is the disk, which is why you see two components under the RAID0 object that is then mirrored under the RAID1 object.  Essentially, the mirror happens at the object level, with is the RAID0 component, so both RAID0 components have to be mirrored.  It boils down to when you have a disk that is > 255GB and your policy is RAID1 FTT1 then that disk will become a RAID10 object, since that's the only way vSAN can effectively handle the multiple sub-components that make up the disk.


Since the other disk is < 255GB, it's only a single component to comprise the object that is the disk, so there is no RAID0 component under the RAID1 component.

View solution in original post

0 Kudos
10 Replies
paudieo
VMware Employee
VMware Employee

vSAN auomatically striped the components for Hard-disk1 ,
it could be that your Hard-disk 1 was greater than 255GB or In cases where a disk group does not contain enough space to hold a VMDK, automatic striping of objects will happen. 

also when you have 3 stripes we dont require a witness component as we use votes for deciding qurum 

This component could end up on the same disk, or on a different disk group, but I cant tell from your screenshot

 

 

 

 

0 Kudos
Tibmeister
Expert
Expert

Yeah, your screenshot just doesn't have enough information.  I don't see any concatenation objects so I don't think you have anything over 255GB in size for a single object/disk.

Without knowing your cluster config, the details of your storage policy, and what the other two columns are (host and fault domain) I don't think we can do anything but guess at what may be going on.  It looks like you may have a strip width of two, or your data disks do not have enough free space to contain everything in one object so it needs to stripe across a couple of objects to complete the disk.

0 Kudos
andvm
Hot Shot
Hot Shot

indeed HDD1 is larger than 255GB

andvm_0-1648745204592.png

 

vSAN default Storage Policy is indeed at Default settings:

andvm_1-1648745266839.png

 

Understand that it will stripe the components into max of 255GB each but why it shows 2x lists of RAID0 for HDD1, why does it not show each component under RAID1 as in case of HDD2 - this is what is not clear to me

0 Kudos
paudieo
VMware Employee
VMware Employee

This is the way vSAN presents the layout, 

We list the components belonging to the mirror underneath to represent that the  mirror made up of components, stripes in this case

Is it the fact do you find it confusing thats throwing you off?

 

 

 

0 Kudos
andvm
Hot Shot
Hot Shot

yes since they are part of the same vSAN policy so expect the layout to be consistent

0 Kudos
Tibmeister
Expert
Expert

So in the case of the disk that's > 255GB, it's getting striped into two objects of equal size, which is a single RAID0 object.  Those two components comprise the single object that is the disk, which is why you see two components under the RAID0 object that is then mirrored under the RAID1 object.  Essentially, the mirror happens at the object level, with is the RAID0 component, so both RAID0 components have to be mirrored.  It boils down to when you have a disk that is > 255GB and your policy is RAID1 FTT1 then that disk will become a RAID10 object, since that's the only way vSAN can effectively handle the multiple sub-components that make up the disk.


Since the other disk is < 255GB, it's only a single component to comprise the object that is the disk, so there is no RAID0 component under the RAID1 component.

0 Kudos
andvm
Hot Shot
Hot Shot

Right, think your explanation made me understand the concept of splitting vdisks larger than 255GB into multiple components forming/showing the RAID 0 which in their entirety are duplicated forming the upper RAID 1 layer 

0 Kudos
TheBobkin
VMware Employee
VMware Employee

"why does it not show each component under RAID1 as in case of HDD2"

Sure it does:

TheBobkin_0-1648824320385.png

 

0 Kudos
andvm
Hot Shot
Hot Shot

yes but I do not need to elaborate, you know what I mean

0 Kudos
Tibmeister
Expert
Expert

It can't be said vSAN isn't verbose and gives you more than enough information, that is for sure.

0 Kudos