ROW targets using something other than Snapshot/CDP
Posted: Fri Mar 01, 2013 4:42 pm
I've been working more with ROW targets, and I'm coming across a fair amount of pain any time I want to update the CDP golden image. Seems like there isn't anything I can do to eliminate the creation of a snapshot when I have the CDP device mounted in growing mode. This makes for quite a bit of wasted space, as others using CDP have found. There's too much management overhead to make a full clone, and even if you do...the cloned disk can't be mounted directly. Possible solutions:
1) Enable ROW modes for Image File Devices (inefficient use of space, but at least you don't have to muck with snapshots all the time)
2) Enable a Snapshot/CDP device mode that DOESN'T CREATE SNAPSHOTS all the time
3) Enable the ability to flatten an existing CDP device and all associated snapshots, since the GUI never seems to find any of these snapshots in the snapshot manager
Additionally, I've been using ramdisks created outside Starwind to hold my ROW targets. It would be really nice to have a ROW mode where the golden image is read into memory from disk, and all per-machine sessions are created in memory as well. I can accomplish this with my kludgey method of making a ramdisk using other software and storing the files on that "drive", but that always results in wasted memory on the host system. It would be nice to have Starwind do this by itself. This is very important from a performance perspective as you add more initiators booting from the same ROW target at or close to the same time. Even storing the CDP files on flash-based PCIe storage devices, which I'm currently doing, can only do so much to help this. If you have 50 machines booting from the device at the same time, you're going to have performance issues with your storage backend. Moving the files to a ramdisk alleviates storage I/O as the bottleneck and moves it to network I/O, which is easier to scale up.
1) Enable ROW modes for Image File Devices (inefficient use of space, but at least you don't have to muck with snapshots all the time)
2) Enable a Snapshot/CDP device mode that DOESN'T CREATE SNAPSHOTS all the time
3) Enable the ability to flatten an existing CDP device and all associated snapshots, since the GUI never seems to find any of these snapshots in the snapshot manager
Additionally, I've been using ramdisks created outside Starwind to hold my ROW targets. It would be really nice to have a ROW mode where the golden image is read into memory from disk, and all per-machine sessions are created in memory as well. I can accomplish this with my kludgey method of making a ramdisk using other software and storing the files on that "drive", but that always results in wasted memory on the host system. It would be nice to have Starwind do this by itself. This is very important from a performance perspective as you add more initiators booting from the same ROW target at or close to the same time. Even storing the CDP files on flash-based PCIe storage devices, which I'm currently doing, can only do so much to help this. If you have 50 machines booting from the device at the same time, you're going to have performance issues with your storage backend. Moving the files to a ramdisk alleviates storage I/O as the bottleneck and moves it to network I/O, which is easier to scale up.
