HiCommand CLIEX

I've been using the HiCommand CLIEX (the extended CLI) today. It differs from the normal CLI in that it talks directly to the array via a command device and bypasses both Storage Navigator and Device Manager. HDS have needed this way of communicating with an array for a long time.

On the one hand, CLIEX is a good thing; the functions are more akin to those offered by EMC's Solutions Enabler in that I can perform direct configuration on the array without an intermediate product. Some of the things I've tried include extracting the actual configuration of an array (which can be obtained in XML format) and creating Host Storage Domains and assigning LDEVs. Although the commands aren't lightning quick (no pun intended), they are certainly quicker than the corresponding commands through Device Manager or Storage Navigator and obviously remove the need to install Device Manager in its entirety. As I'm running tests against a new array, I want to create lots of HSDs (one per FEP) and assign a separate LDEV to each. CLIEX saved me a lot of time (especially as I haven't got a Device Manager up yet).

On the negative side, the commands are powerful and "delete" functions give no warning or final check; so at your peril use the delete functions! I checked removing an LDEV while running (a lot) of I/O to a LUN and the command was bounced, however when the I/O was reduced (but the LUN still technically in use), I was able to pull the LDEV away with the obvious consequences. Also, these commands talk directly to the array and appear to bypass the configuration on the SVP. If you make a CLIEX change followed up by a Storage Navigator change without first having refreshed SN, then you simply overwrite the CLIEX changes (I know, I tried it).

One little bugette I found... The CLIEX command hdvmcliex is actually a batch file, so if you want to call the command from within a batch script you need to prefix with the "CALL" command.

I can see the CLIEX interface could be extremely useful. I intend to use it to mass configure a USP from scratch. In addition, I can also see how it could be useful to create dynamic failover scripts (more on this in a future post) without the need for Device Manager to be running. However HDS need to beef up the security around the product to prevent inadvertent allocation and deallocation gotchas. They also need to consider moving the locking mechanism (which allows a reserve to be taken on the SVP and prevent SN/CLIEX/Device Manager clashing configuration changes) to being a specific CLIEX command rather than relying on the Device Manager locking function.

One final thought... I'm not sure of any additional security to prevent any user with a command device from installing and running CLIEX and trashing an entire array. Unless you know otherwise?

Mine's bigger than yours - do we care?

Our resident storage anarchist has been vigorously defending DMX - here. It's all in response to discussions with Hu regarding whether USP is better than DMX. Or, should I say DMX-3 and Broadway (whoops, I mentioned the unmentionable, you'll have to shoot me now).

I have to say I enjoyed the technical detail of the exchanges and I hope there will be a lot more to come. Any insight into how to make what are very expensive storage subsystems work more effectively has to be a good thing.

But here's the rub. Do we care about how much faster DMX-3 is over USP? I doubt the differences are more than incremental and as I've both installed, configured and provisioned storage on 9980V/USP/8730/8830/DMX/DMX2/DMX3, I think I've enough practical experience to qualify it. (By the way, I loved StorArch's comment about how flexible BIN file changes are now. Well, they may be, but in reality I've found EMC cumbersome to release configuration changes).

Finally I'll get round to the point of this post; most large enterprise subsystems are of the same order of magnitude of performance. However I've yet to see any deployment where performance management is executed to such a degree that, hand on heart, the storage admins there can claim they sequeeze 100% efficient throughput. I'd make an estimate that things probably run 80% efficient, with the major bottlenecks being port layout, backend array layout and host configuration.

So the theoretical bantering on who is more performant than the other is moot; now, EMC, HDS or IBM, come up with a *self tuning* array then you've got a winner...