Im not sure if this is the right category or if its even a VMware question but I was wondering what people are doing with their storage to setup with VMware when it comes to arrays. We just got an IBM DS3512 SAN devices with 12TB of storage and Im trying to figure out how to set it up. We used NetApps with Xen before and this is totally different. These are going to be used for around 12-15 VMs and file storage.
My main question is what is recommended for setting up arrays and logical drives? Should I make one big array for the whole capacity of the SAN? or one for VMs and one for file storage? What is the benefit of having multiple arrays? Also, how does VMware use logical drives for storage? Do you make a logical drive for a group of VMs? A single VM? So many questions, so little time.
Im new to this so any recommendations on the best storage setup would be great.
ESX(i) doesn't recognize LUNs greater than slightly less than 2TB so you will at least need to carve up the storage accordingly. It is possible to combine several LUNs to create larger datastores. NFS is different and you can use 16TB shares presented to ESX(i).
Thanks for the link. Now I have even more reading to do!
One other thing I was wondering about is how many iSCSI connections are needed for our setup. Our storage has 4 iSCSI ports on each of the 2 controllers and our blades have 4 network ports each. We have 2 blades that we are using with this storage and some others that most likely wont connect to it. I also read you should cross connect between 2 different switches with your iSCSI connections.
While you could theoretically make the whole thing work using only a single connection, multiple links are recommended to increase throughput as well as redundancy. That's the reason why it's suggested that you route through separate switches -- if one of the switches happened to fail, you'll still have connectivity through the other one (or more).
So we got arrarys made and within those some logical drives that dont exceed 2 TB. What Im not sure about is what is the difference between a logical drive an a LUN or is it just vendor terminology? After making the logical drives they can be seen in Vcenter. Are they considered LUNs by VMware?
One more question.... I think.
As for making datastores from your LUNs is there any reason to carve them up into multiple datastores rather than one big datastore? Does it affect performance or disaster recovery etc?
Yes, it does for exapmple one large datastore for all virtual machines would result in more SCSI Reservations where the ESX hosts would have to struggle to get the lock on the VM files.
Also note that one large datastore would also affect the Recovery Time Objective (RTO) because the lager the datastore the longer it would take to recover the datastore.
In short I wouldnt suggest creating one VM to datastore mapping, this is needed only when the I/O usage is too high.
We have 2 logical drives around 2TB each and want to know how to carve them up for datastores for the best performance. Or should our logical drives be smaller? And are the logical drives LUNs to VMware?
NO, I dont suggest creating one datastore for one VM it would result in too much management issues etc. To take this decision you should know the IOPS and latency that is suggested for the applications that you would use in the VMs. So lets say if you have a VM with some application which needs high IOPS and very less latency you may keep it in a separate datastore but if you have VM which are not so high IO intensive then you may group them in one datastore.
Refer to How Many Virtual Machines Can Share the Same LUN section from the http://www.vmware.com/files/pdf/scalable_storage_performance.pdf
I hope all this informaiton helps