Verifying that you need 10.9?   If so those will definitely have to be vm's.

The above machines that are being replaced are:

[build9-m4] out:       Model Identifier: MacPro6,1
[build9-m4] out:       System Version: macOS 10.12.2 (16C68)

[build48-m4] out:       Model Identifier: MacPro6,1
[build48-m4] out:       System Version: macOS 10.12.2 (16C68)

[build190-m4] out:       Model Identifier: Macmini7,1
[build190-m4] out:       System Version: macOS 10.12.2 (16C68)

[build554-m4] out:       Model Identifier: MacPro6,1
[build554-m4] out:       System Version: OS X 10.10.5 (14F1808)

[build555-m4] out:       Model Identifier: MacPro6,1
[build555-m4] out:       System Version: OS X 10.11.6 (15G31)

[build556-m4] out:       Model Identifier: MacPro6,1
[build556-m4] out:       System Version: macOS 10.12.2 (16C68)

[build557-m4] out:       Model Identifier: MacPro6,1
[build557-m4] out:       System Version: macOS 10.12.2 (16C68)

[vm1026-m4] out:       Model Identifier: VMware7,1
[vm1026-m4] out:       System Version: macOS 10.12.2 (16C68)

10.9 is OK as VM, thank you!

We actually need 10.9 through 10.12 to replicate the testers in the main waterfall (even there, I believe 10.9 is a vm, so that should be okay)

I am not sure about why the current distribution of machines is the way it is, i.e. one 10, one 11 and six 12s

Jeff, do you know?

The distribution should follow the number of variable builders needed for each configuration. e.g. in Findit's config i see only 1 unique variable builder that is to cover 10.11 (mac_chromium_variable_10.11), so only 1 machine for that configuration should be plenty. It seems most builders on the main waterfall are mostly on 10.9 or 10.12 (though I didn't check all of them), with only a few on 10.10/11 so this distribution I think is ok

The following revision refers to this bug:
  https://chrome-internal.googlesource.com/chrome-golo/chrome-golo/+/ea75b2dd6a482d5c6f9b7bc28133baa42f1edef6

commit ea75b2dd6a482d5c6f9b7bc28133baa42f1edef6
Author: Peter Schmidt <pschmidt@google.com>
Date: Mon Jan 08 18:12:01 2018

I just noticed that there are 2 x 10.12 swarming slaves in luci.chromium.findit   

$ swarming.py bots -d os "Mac-10.12" -d pool "luci.chromium.findit" -S https://chromium-swarm.appspot.com  --bare
build11-m4
build12-m4

Did you require an additional 2 more?

10.9 will have to be vm's.  Also for now the 10.10/10.11 swarming slaves will also be vm's.

I think we are good with those for now.

The following revision refers to this bug:
  https://chrome-internal.googlesource.com/infradata/config/+/be40725ee1fab1acad0adc22b64a64e1906cbd9c

commit be40725ee1fab1acad0adc22b64a64e1906cbd9c
Author: Peter Schmidt <pschmidt@google.com>
Date: Mon Jan 08 19:45:02 2018

$ swarming.py bots -d os "Mac" -d pool "luci.chromium.findit" -S https://chromium-swarm.appspot.com

build11-m4
  {"caches": ["builder_59903421b573f7977c3041901e2faa9f9ce8ebb7dd836cd37859417a96cc2630", "builder_6172fd349d5e99286697eb1d4a38d44c914f9c6da8c557210c46dd1eb45d022f", "builder_b690363533dae902654ad3d0893c58500cff481f870cf4ff9ed21199d073c9d7", "builder_eace6e472045c8569ae029807ce0d032be6133ca88eb58adfc5edf57ca5909bd", "builder_f6b8a5f7db8ea5becd9a25993722164fc3419fa0c4b71667d78cce3a185d0da5", "git", "goma", "vpython", "win_toolchain"], "cores": ["24"], "cpu": ["x86", "x86-64", "x86-64-E5-2697_v2"], "gpu": ["1002", "1002:679e", "1002:679e-4.0.11-3.2.8"], "hidpi": ["0"], "id": ["build11-m4"], "mac_model": ["MacPro6,1"], "machine_type": ["n1-standard-16"], "os": ["Mac", "Mac-10.12", "Mac-10.12.2"], "pool": ["luci.chromium.findit"], "python": ["2.7.10"], "ssd": ["1"], "xcode_version": ["8.0"]}

build12-m4
  {"caches": ["builder_59903421b573f7977c3041901e2faa9f9ce8ebb7dd836cd37859417a96cc2630", "builder_6172fd349d5e99286697eb1d4a38d44c914f9c6da8c557210c46dd1eb45d022f", "builder_eace6e472045c8569ae029807ce0d032be6133ca88eb58adfc5edf57ca5909bd", "git", "goma", "vpython", "win_toolchain"], "cores": ["24"], "cpu": ["x86", "x86-64", "x86-64-E5-2697_v2"], "gpu": ["1002", "1002:679e", "1002:679e-4.0.11-3.2.8"], "hidpi": ["0"], "id": ["build12-m4"], "mac_model": ["MacPro6,1"], "machine_type": ["n1-standard-16"], "os": ["Mac", "Mac-10.12", "Mac-10.12.2"], "pool": ["luci.chromium.findit"], "python": ["2.7.10"], "ssd": ["1"], "xcode_version": ["8.0"]}

vm26-m9
  {"cores": ["8"], "cpu": ["x86", "x86-64", "x86-64-E5-2697_v2"], "gpu": ["none"], "id": ["vm26-m9"], "mac_model": ["VMware7,1"], "machine_type": ["n1-highcpu-8"], "os": ["Mac", "Mac-10.9", "Mac-10.9.5"], "pool": ["luci.chromium.findit"], "python": ["2.7.5"], "xcode_version": ["5.1.1"]}

vm27-m9
  {"cores": ["8"], "cpu": ["x86", "x86-64", "x86-64-E5-2697_v2"], "gpu": ["none"], "id": ["vm27-m9"], "mac_model": ["VMware7,1"], "machine_type": ["n1-highcpu-8"], "os": ["Mac", "Mac-10.9", "Mac-10.9.5"], "pool": ["luci.chromium.findit"], "python": ["2.7.5"], "xcode_version": ["5.1.1"]}

vm28-m9
  {"cores": ["8"], "cpu": ["x86", "x86-64", "x86-64-E5-2697_v2"], "gpu": ["none"], "id": ["vm28-m9"], "mac_model": ["VMware7,1"], "machine_type": ["n1-highcpu-8"], "os": ["Mac", "Mac-10.10", "Mac-10.10.5"], "pool": ["luci.chromium.findit"], "python": ["2.7.10"], "xcode_version": ["7.0"]}

vm29-m9
  {"cores": ["8"], "cpu": ["x86", "x86-64", "x86-64-E5-2697_v2"], "gpu": ["none"], "id": ["vm29-m9"], "mac_model": ["VMware7,1"], "machine_type": ["n1-highcpu-8"], "os": ["Mac", "Mac-10.10", "Mac-10.10.5"], "pool": ["luci.chromium.findit"], "python": ["2.7.10"], "xcode_version": ["7.0"]}

vm30-m9
  {"cores": ["8"], "cpu": ["x86", "x86-64", "x86-64-E5-2697_v2"], "gpu": ["none"], "id": ["vm30-m9"], "mac_model": ["VMware7,1"], "machine_type": ["n1-highcpu-8"], "os": ["Mac", "Mac-10.11", "Mac-10.11.6"], "pool": ["luci.chromium.findit"], "python": ["2.7.10"], "xcode_version": ["8.0"]}

vm31-m9
  {"cores": ["8"], "cpu": ["x86", "x86-64", "x86-64-E5-2697_v2"], "gpu": ["none"], "id": ["vm31-m9"], "mac_model": ["VMware7,1"], "machine_type": ["n1-highcpu-8"], "os": ["Mac", "Mac-10.11", "Mac-10.11.6"], "pool": ["luci.chromium.findit"], "python": ["2.7.10"], "xcode_version": ["8.0"]}

Thank you!