Flash Copy, VMFS3 volume sizing

[upg3]

Has any one enabled Flash Copy on DS4700 for the ESX logical volume, does it support Flash Copy or any issue may occur if I configure it.

I do have 3 VSP host and would use around 18 VM's on DS4700 how many logical drive should use to get optimal performance. Should I use one volume to each Host or single logical volume to all servers or any other configuration would be useful. Earlier I was trying to use one 2TB volume then came to know it cannot use 2TB at a stretch.

[AndreTheGiant]

There isn't a simple answer, cause it depends on:

Storage best practice

Storage type and disks type

VM number, size and type of I/O

Max VM and I/O per LUN

Max LUN size (less than 2 TB - 512B)

Generally it's not a good idea to have very large LUNs: when you have a large number of VMs on a single VMFS based block device you will see a higher level of SCSI Reservation Conflicts which always results in performance degregation.

This occurs because the clustered VMFS LUN uses a file lock control function from the hosts and the higher the VM count the more often they have to wait on each others update housekeeping I/O activity.

Usually a value between 400-800GB could be reasonable.

Here are some good threads that talk about this....

LUNS Size - http://www.vmware.com/community/thread.jspa?threadID=36725

Sizing LUN for enough free space after VM - http://www.vmware.com/community/thread.jspa?messageID=649338

Smaller LUNS or Larger LUNS - http://www.vmware.com/community/thread.jspa?threadID=90203

Larger LUNS = More Disks = More Performance - http://www.vmware.com/community/thread.jspa?threadID=84843&tstart=0

RAID Recommendations for local disk - http://www.vmware.com/community/thread.jspa?messageID=622456

RAID 5/6 Scaling - http://www.vmware.com/community/thread.jspa?messageID=718641

Which is better, more or fewer disks - http://www.vmware.com/community/thread.jspa?messageID=599611

SAN Configuration Guide - http://www.vmware.com/pdf/vsphere4/r40/vsp_40_san_cfg.pdf

SAN Conceptual and Design Basics - http://www.vmware.com/pdf/esx_san_cfg_technote.pdf

Andre

[upg3]

What about the Flash Copy, can I enable it on VMFS logical volumes.....or I have to take care any of the configuration parameters before doing it.

[AndreTheGiant]

I do not use IBM storage very much...

So I'm not sure, but seems tahat you can use it...

Be only sure to do not give the "snapshot" at the same ESX that has the original volume!

Andre