Is there a limit to the number of guests that can boot from a single iso?

We are experiencing intermittent problems booting some number of VM guests from a single boot iso. Not exactly sure what that number is but it seems at some point we get the following messages for each guest....

CDROM: Connecting ide1:1 to '/vmfs/volumes/4ff5e4ea-bab8f89e-9aaf-d4856456c12b/Boot-ISO/XDBoot_PVS_2v-1v.iso'. img=1 raw=0 remote=0

2012-08-29T13:50:13.706Z| vcpu-0| FileIOErrno2Result: Unexpected errno=87, Too many users

2012-08-29T13:50:13.706Z| vcpu-0| AIOGNRC: Failed to open '/vmfs/volumes/4ff5e4ea-bab8f89e-9aaf-d4856456c12b/Boot-ISO/XDBoot_PVS_2v-1v.iso' : Too many users (5700000002) (0x2001).

2012-08-29T13:50:13.706Z| vcpu-0| CDROM-IMG:  image open for '/vmfs/volumes/4ff5e4ea-bab8f89e-9aaf-d4856456c12b/Boot-ISO/XDBoot_PVS_2v-1v.iso' failed: Too many users (5700000002).

2012-08-29T13:50:13.706Z| vcpu-0| CDROM-IMG: Failed to connect '/vmfs/volumes/4ff5e4ea-bab8f89e-9aaf-d4856456c12b/Boot-ISO/XDBoot_PVS_2v-1v.iso'.

2012-08-29T13:50:13.706Z| vcpu-0| CDROM: Failed to connect CDROM device '/vmfs/volumes/4ff5e4ea-bab8f89e-9aaf-d4856456c12b/Boot-ISO/XDBoot_PVS_2v-1v.iso'.

2012-08-29T13:50:13.706Z| vcpu-0| Msg_Post: Warning

2012-08-29T13:50:13.706Z| vcpu-0| [msg.cdromImage.cantOpen] Cannot connect file "/vmfs/volumes/4ff5e4ea-bab8f89e-9aaf-d4856456c12b/Boot-ISO/XDBoot_PVS_2v-1v.iso" as a CD-ROM image: Too many users

2012-08-29T13:50:13.706Z| vcpu-0| [msg.device.startdisconnected] Virtual device ide1:1 will start disconnected.

Sometimes we reboot and it works fine other times not. If we redirect to a different copy of the ISO it will work. Is there a parameter that can be set to allow for greater number of concurrent connections to an ISO. Any thoughts would greatly be appreciated.   BTW we are running VirtualCenter 5.0.0 and ESXi version 5.0.0....Thanks

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Have been experiencing this very issue with ESXi 4.1 U2.

Had a look in my /var/log/messages and discovered FS3 error messages described below.

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I believe in 4.x and 5.x the limit was 32 VMs that can have a file handle open.  In 5.1 that increases to (I believe) 128.  Also, in 4.x and 5.0, no more than 8 hosts can access a given file.  In 5.1 this is increased to 32.

It is not, however, a tuneable parameter.

A better way to do what you are attempting might be PXE boot - no limit on that.

--Matt VCDX #52
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