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gilad_benjamini
Contributor
Contributor

Stability problems with ext3 on host

I have a few guests with ext3 used for their root file system. Since these VMs are used for kernel development, they tend to crash several times a day.

Frequently the VMs cannot start because of corruption of the root filesystem. The linux explicitly asks for manual fsck.

This rather surprised me. On physical machines I don't think I have seen this even once with ext3. Machines would boot up, throw some wording about fixed problems and continue to their business.

Any thoughts on this ?

The VMs and their disks are located on NAS which is accessed by NFS. Could that be the weak link ?

Thanks

Gilad

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3 Replies
Texiwill
Leadership
Leadership

Hello,

If you are crashing VMs then there is always a chance that the VMDK is corrupt. THis used to happen to me more on physical machines than virtual machines however. So my experience is the reverse of what you are seeing. Any crash can cause this on physical or virtual. I think you just got lucky in the physical world.

One thing you can do is to not repair, but to throw away the vmdk, deploy from template, etc. Or if they are going to do something that could crash the system use a snapshot, then throw away the snapshot when done. That may help....


Best regards,

Edward L. Haletky

VMware Communities User Moderator

====

Author of the book 'VMWare ESX Server in the Enterprise: Planning and Securing Virtualization Servers', Copyright 2008 Pearson Education.

CIO Virtualization Blog: http://www.cio.com/blog/index/topic/168354

As well as the Virtualization Wiki at http://www.astroarch.com/wiki/index.php/Virtualization

--
Edward L. Haletky
vExpert XIV: 2009-2023,
VMTN Community Moderator
vSphere Upgrade Saga: https://www.astroarch.com/blogs
GitHub Repo: https://github.com/Texiwill
gilad_benjamini
Contributor
Contributor

I accept most of what you say, but I am still trying to understand.

First, in the physical world, I have seen many crashes with ext3 and the freqency of problems was a lot lower.

Second, I have seen similar problems when we had stability problems with our host or storage.

In any case I would expect ext3 to provide a more robust file system

  • The subject of this thread, btw, is wrong. I meant ext3 on the guest

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mike_laspina
Champion
Champion

Hello,

I have experianced this from time to time. The real issue here is the virtual controller and virtual host behavior.

When the VM writes to a virtual disk the command may not be flushed to the file immediately and this will at some point cause some inconsistancies in files system transactions if it occures frequently.

Some OS drivers can initiate a scsi command option to request that the data be flushed to disk immediatelly the vmware tools driver supports this request and will not report a successfull write until the operation is complete.

This scsi command is used by DB's like MSSQL, Oracle and other well matured apps.

http://blog.laspina.ca/ vExpert 2009
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