Accepted Solutions
'tuck,
>>Do we need to have another LUN for (equallogic) server snapshots?
No. When you create a volume on your Equallogic SAN it will by default reserve the same amount of space again for Snapshots. You can at any time increase or decrease this reserved space. Should you consume this reserved space the default action is to delete the oldest snapshot.
>>Can you initially define 1 LUN with a limited amount of space (say 1.5 TB) and then expand it out later if needed, and add additional LUNs when needed?
Yes, but you might not want to do this. Yes you can create a volume of 1.5TB, and later increase it size, but it's new size will not automatically be recognized by the OS. Off hand I don't believe VMFS (VMware file system) will stretch to see the increased space at all, so your option here is to create a second volume and to make an extent and thereby creating one big volume. The downside of this is that should anything happen to any of the targets in a datastore made of extents ALL the data is lost. I am of the opinion that extents are bad - they do have there place, and there they should be kept.
However, lets say you know that in the future a particular target (LUN) will need to be bigger, but given that you only have 7TB of space you can't afford to provide it will all it needs. For example a fileshare, you know over time people are just going to store more and more, this is where you could present a volume of a large size, say 2TB, but it would only consume as much space as the data been stored required, as more data is written more space is required. This is referred to as thin provisioning, it is a double edged sword. If you over use thin provisioning by presenting every volume as thinly provisioned and therefore present 70TB of storage from your 7TB array, which you can do 
but if you neglect to submit that purchase req in time to buy and rack the additional storage beyond 7TB before people start writing to it, you are going to cause your self some pain as OSes don't like been told they can't write no more!
Do take a step back and figure out your LUN layout, but don't over thing it, with Storage VMotion you can always relocate VMs. I would advise against creating one BIG volume and sticking all your VMs on it, rather I would stick with ~500GB volumes and spread them out. Do leave some slack space per volume for the use of VM snapshots.
>>Are LUNs assigned based upon disk drives, or storage, or both?
It is not clear to me what your question here is, please clarify, but to confuse the issue Equallogic arrays don't present LUNs, but presents targets, but I think from your perspective there isn't a difference.
You may want to pick up a copy of http://www.amazon.com/VMware-Infrastructure-Advanced-Technical-Operations/dp/0971151083
With regards to RAID setup, if you feel you've gotten it wrong you can always change it without loss of data, you can set it per LUN or let it default to what you choose for the entire array.
Good luck.
'tuck,
>>Do we need to have another LUN for (equallogic) server snapshots?
No. When you create a volume on your Equallogic SAN it will by default reserve the same amount of space again for Snapshots. You can at any time increase or decrease this reserved space. Should you consume this reserved space the default action is to delete the oldest snapshot.
>>Can you initially define 1 LUN with a limited amount of space (say 1.5 TB) and then expand it out later if needed, and add additional LUNs when needed?
Yes, but you might not want to do this. Yes you can create a volume of 1.5TB, and later increase it size, but it's new size will not automatically be recognized by the OS. Off hand I don't believe VMFS (VMware file system) will stretch to see the increased space at all, so your option here is to create a second volume and to make an extent and thereby creating one big volume. The downside of this is that should anything happen to any of the targets in a datastore made of extents ALL the data is lost. I am of the opinion that extents are bad - they do have there place, and there they should be kept.
However, lets say you know that in the future a particular target (LUN) will need to be bigger, but given that you only have 7TB of space you can't afford to provide it will all it needs. For example a fileshare, you know over time people are just going to store more and more, this is where you could present a volume of a large size, say 2TB, but it would only consume as much space as the data been stored required, as more data is written more space is required. This is referred to as thin provisioning, it is a double edged sword. If you over use thin provisioning by presenting every volume as thinly provisioned and therefore present 70TB of storage from your 7TB array, which you can do but if you neglect to submit that purchase req in time to buy and rack the additional storage beyond 7TB before people start writing to it, you are going to cause your self some pain as OSes don't like been told they can't write no more!
Do take a step back and figure out your LUN layout, but don't over thing it, with Storage VMotion you can always relocate VMs. I would advise against creating one BIG volume and sticking all your VMs on it, rather I would stick with ~500GB volumes and spread them out. Do leave some slack space per volume for the use of VM snapshots.
>>Are LUNs assigned based upon disk drives, or storage, or both?
It is not clear to me what your question here is, please clarify, but to confuse the issue Equallogic arrays don't present LUNs, but presents targets, but I think from your perspective there isn't a difference.
You may want to pick up a copy of http://www.amazon.com/VMware-Infrastructure-Advanced-Technical-Operations/dp/0971151083
With regards to RAID setup, if you feel you've gotten it wrong you can always change it without loss of data, you can set it per LUN or let it default to what you choose for the entire array.
Good luck.