How to extend ISCSI storage domain?

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I have added a lun extend in my storage cluster, in RHEVM data center,only can see the original size, how to extend ISCSI storage domain online?

Responses

RHEVM does not support extending luns at the iSCSI san or FCP san to resize the storage domain.

 

To extend a storage domain, please create a new lun on the storage and extend the storage domain using that new lun using  Storage -> Select the storage domain and "Edit" option from RHEV_M.

actually, I dit lun extend online, I just want to know the official howto:

 

The major procedure was:

 

1.in storage create a lun extend

2.ssh to hypervisor

3. run: cat 1 > /sys/block/sdb/device/rescan , then fdisk -l can see /dev/sdb has the new size

4. run: multipathd -k, del path sdb, add path sdb, resize map 360022a110004fac76f2a4c8e00000017

5.run: multipath -ll can see 360022a110004fac76f2a4c8e00000017 has the new size

6. run: pvresize /dev/mapper/360022a110004fac76f2a4c8e00000017

7.run :pvdisplay  can see /dev/mapper/360022a110004fac76f2a4c8e00000017 has the new size

8. set hypervisor to maintance mode and active it again

9: in RHEVM, can see iscsi storage domain has the new size

RHEV does not support changes to LUN sizes. The correct way of doing it is to create an additional LUN, and add it to the existing domain.

This will effectively create a new PV and add it to the existing VG, thus making it larger. What you have done is not the supported way.

 

Honestly, this is as bad as vmware. The reason I hate the supported solution is really when you are adding a PV to the existing VG, you are spanning across two PV's or more... BAD BAD BAD. If one of those PV's goes belly up you'll potentially lose everything.

 

I agree with the resize.

 

However, since it is not supported I suggest creating a new target with the correct size that you want and migrating all of the virtual machines to the new VG... every VG should only contain one LUN/PV in my opinion. Otherwise you'll just introduce future nightmares.

Thank you for the input David.

 

I do agree that resizing LUNs should be supported, and if this is important for you and your company, please file an RFE through support - the more of those come in - the more weight this feature will have when engineering resources are distributed. 

 

As for a single PV per VG best practice - it might not be the only right way to do it. I do recall several cases where the SAN vendor recommended using multiple small LUNs instead of one large LUN for specific types of loads, to increase performance, and for other reasons I can't recall atm.