withjigs
Contributor
Contributor

Bus sharing vs Multi-writer

Hi All,

I am trying to understand the difference between SCSI bus sharing and Multi-writer locking.

What are some use cases of each.

Thank you in advnace.

Jigar

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4 Replies
golddiggie
Champion
Champion

IIRC, the sharing is used when you build MS failover clusters on VMware VMs. That's part of what allows you to share the RDM volume between two (or more) VMs.

Are you just looking at different settings, or are you actually trying to build something specific?? Also IIRC, there's decent documentation that describes pretty much every item you can change in a VM's virtual hardware/setup.

Hosted Systems Engineer IV (VMware environment)
Brewing beer again!
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vmrale
Expert
Expert

withjigs,

look at this KB VMware Knowledge Base.​ It describes the nuances pretty simple.

Regards
Radek

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basteku73
Enthusiast
Enthusiast

I'm also looking for differences between bus sharing and multi-writer mode.

This KB which you linked, actually doesn't explain differences.

In fact I think, that maybe for MS Clustering and RDMs is used scsi bus sharing, and for other cluster solutions based on other operating systems like linux, oracle is used Multi-writer. Is this correct ?

Regadrs,

Sebastian

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basteku73
Enthusiast
Enthusiast

Ok,

I found explanation Smiley Happy

"SCSI bus sharing allows multiple VMs to open the same shared virtual disks or RDMs concurrently. To prevent concurrent writes to the shared disks, the Guest Operation System must provide the functionality that elects which node in the cluster is allowed to write to the shared disks. This is provided by Windows Server Failover Clustering and the use of quorum disks. This is in contrast to utilizing multi-writer locking, which allows up to eight hosts to concurrently lock a virtual disk. "

I found this in a book "Storage Design and Implementation in vSphere 6: A Technology Deep Dive" written by Mostafa Khalil.

Regards,

Sebastian

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