I was talking to a fellow consultant today. He ran into the following error messages at one of his customer sites:
vmkernel: 8:18:59:58.640 cpu2:1410)WARNING: Heap: 1370: Heap_Align(vmfs3, 4096/4096 bytes, 4 align) failed. caller: 0x8fdbd0
vmkernel: 8:18:59:58.640 cpu2:1410)WARNING: Heap: 1266: Heap vmfs3: Maximum allowed growth (24) too small for size (8192)
During the conversation I knew I’d seen this problem before. But the problem that I witnessed was related to a high threshold value in Vizioncore vFoglight. I knew it was possible to change the setting:
- Open vCenter, and click a specific host
- Click on the “Configurations” tab
- Click on Advanced Settings, VMFS3
- Change the value of “VMFS3.MaxHeapSizeMB”
The default value is 16MB, this allows for a maximum of 4TB of open vmdk’s on a single host. The max setting is 128MB which allows for a maximum of 32TB of open vmdk’s on a single host. Keep this in mind when designing your environment.
Keep in mind that this is ESX 3.5 only, you can’t change the heap size in ESX 3.0.x.
Jason Boche says
vFoglight comes from Vizioncore, not Veeam.
Adam Baum says
I think you left out a step…don’t you need to click on Advanced Settings to get to the VMFS3 options?
Craig Haskett says
Does this have more to do with the number of files, rather than the total size of vmdk’s open?
We have not adjusted this setting, and have several hosts that have 4TB+ of open vmdk’s, and have never had this error logged.
Excellent, exactly what we needed. Thanks for the post.
Mikael M. Hansen says
In november we learned about this the hard way.
A linux file server crashed and trashed the disks so badly that we needed to reinstall.
All because VMware only allocates up to a certain amount of storage for addressing of vmdk’s. We suggested to to the support engineer that the size should be allocated “as needed” rather that some konfigurable size set by the user. Have not gotten any respons though…
Recently i faced the same issue with my client, I am able to solve. While doing a research on this VMFS heap size, i came across a blog
In short this blog says, the VMFS heap size and the open VMDK file size for the esxi host is related with VMFS block size. In vsphere 4 if the block size is more than 1 MB, then the esxi host can have more than 25TB of open VMDK.
Could you please give more insight on this.
My thought in this issue is, from the consolidation perspective this factor really matters. Now a days the 1 TB RAM, HP ProLiant DL980 8 socket, are common in the big datacenters, so with VMware if we want to achieve more consolidation this is a bottleneck. I hope the VVOLS can solve these.
Please share your thoughts, from VMware side.