VMware - Snap with care
Did you know that if you snapshot a server in VMware the snap files are kept with the server?
So what you say. Well if you have some tiered storage and your nice super-duper SQL box has system drive on some slow SATA storage and your Logs and Data are nice fast SAS or FC storage when you snap all the writes will go to the slow storage and your SQL box will run like a complete dog, not a greyhound but three legged pug with a bad hip.
You can if you so wish specify where VMware stores it’s snap files but you will always see performance problems as it switches between locations to provide the latest data.
VMware snapshots should be seen as a very short term thing, i.e. snapshot, do update. does it look ok, remove snapshot or revert, anything more than a couple of hours and you are starting to go in to dodgy performance territory particularly on SQL boxes and I would guess nything else running a database like Exchange or Oracle.
One useful tool to have in your armoury is RVTools written by Rob De Veij. This is simple VMware DB query tool that reports back what the state of all your VMs are. It provides a tab interface with key metrics such as any snapshots, server health that will include delights such as disk usage and filename inconsistencies, what is stored on which VMFS partition etc. a great tool and it is freeware to boot. This was recently updated to version 3 and should be on any VMware admins desktop.
So what you say. Well if you have some tiered storage and your nice super-duper SQL box has system drive on some slow SATA storage and your Logs and Data are nice fast SAS or FC storage when you snap all the writes will go to the slow storage and your SQL box will run like a complete dog, not a greyhound but three legged pug with a bad hip.
You can if you so wish specify where VMware stores it’s snap files but you will always see performance problems as it switches between locations to provide the latest data.
VMware snapshots should be seen as a very short term thing, i.e. snapshot, do update. does it look ok, remove snapshot or revert, anything more than a couple of hours and you are starting to go in to dodgy performance territory particularly on SQL boxes and I would guess nything else running a database like Exchange or Oracle.
One useful tool to have in your armoury is RVTools written by Rob De Veij. This is simple VMware DB query tool that reports back what the state of all your VMs are. It provides a tab interface with key metrics such as any snapshots, server health that will include delights such as disk usage and filename inconsistencies, what is stored on which VMFS partition etc. a great tool and it is freeware to boot. This was recently updated to version 3 and should be on any VMware admins desktop.
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