VMax Deferred Maintenance

The idea is to put a bunch of spares in the box and send the CE to harvest the bad ones when the spare count gets low.  I'm not sure what "low" is, but I might want them to come out when there was at least one left. 

I'm not familiar with this "deferred maintenance" option you are asking about, but I am anxious to hear the answer if anyone else knows what this is. When you say it is "enabled on the VMax" what exactly do you mean by that. Is it an option you see somewhere in one of the interfaces? If so it doesn't make a lot of sense that it would relate to when EMC comes to perform service. Actually the way you describe it doesn't make a lot of sense to me in general. I can't imagine what the purpose would be of not having them come in until you were out of hot spares. If that were the case there wouldn't be a lot of point in having multiples because you would always eventually end up in a state where there was more risk than there should be.

Anyway, hopefully someone can comment on what this is and put all our minds at ease :-)

What is advantage to customer?

Less touch points on the system.  CE is more rested.

Less cost to EMC which hopefully would result in lower costs to the customer.

Less touch points on the system.  CE is more rested.

It looks like things changed a lot ... Now EMC wants "rested" CEs ??

Hi Stefano,

It is very nice to hear from you. Please refer to the similar thread https://community.emc.com/thread/102140?tstart=0 for more details on deferred maintenance. This thread was on DMX, but it essentially the same feature on both products (except that VMAX does not have dynamic or "standard" sparing, just permanent). I know that Engineering are still planning to adjust the threshold so EMC gets a dial home before the spares pool is depleted. I will ask the EMC Corporate System Engineer responsible for deferred maintenance to respond to this thread with the latest advice.

Best Regards,

Michael.

Thank you for the responses. Primus emc212019 is helpful and looks to support my statements below and examples in my first post.

- Currently EMC will not automatically go out and replace the failed drives until the spares are completely depleted for that particular drive type. There is a time between the last disk failure and CE replacing the drives when you are running with no spares.

- Currently there is no way to change this threshold except to disable "deferred maintenance".

Did the replies to your post answer your questions? If so, please mark the helpful and correct posts and also mark the post as answered. Doing so helps others identify the most useful posts. Thank you.

No they are not at risk.  When there is no permanent spare available for any drive in the array a case is generated for replacement of the failed disk drives.  There can still be spares in the array that can be used as a stadnard hot spare just not a permanent spare.

Is this true even on the VMax which only does permanent sparing?

Thank you for reminding about VMAX sparing.  Sometimes I think I deal with too many products.

So, things are much clearer than they were when this thread started, but I too have a difficult time allowing the assesment of "no additional risk" in allowing a zero hot spare available state.

If there is no risk in allowing a "Zero Hot Spare available" state then why would anyone waste money on putting in hot spares in the first place?

I can understand that the difference might be minimal, but it is ABSOLUTELY greater than the risk involved if Hot Spares ARE available. I could never justify spending the money on a highly redundant highly available system like the Symmetrix and then purposely allow a state where there is no immediately available redundancy if there was an option.

I am glad to see this being reviewed again. Coincidentally I am in the process of reading "The Black Swan - The Impact of the Highly Improbable" by Nassim Taleb - http://en.wikipedia.org/wiki/Black_swan_theory.

After the previous discussions, our recommendation (which our clients have readily agreed to) has been to NOT enable deferred service. Allen W has a good point - `If there is no risk in allowing a "Zero Hot Spare available" state then why would anyone waste money on putting in hot spares in the first place?`

Following on from that, if `After very careful analysis it was found that the new process did not impose any additional risk` (quoting 2gnWoUR4Wl1186674120175), then why take the trouble to modify the microcode, so a `customer can chose (sic) to change the criteria from zero to one in which we call the spares out for replacement` ?

Hi, I would like to clarify one point here, Deferred maintenance will not wait for the spare count ot go down to 0 before calling the CE for replacement....

There is a concept of covering spare, Every drive has a covering spare drive assigned to it, In case that drive fails, the covering spare drive will take its place, this is not a 1-1 mapping, Onec spare will cover multiple disks. When enguinity detects that any disk does not have any covering spare it will call home and generate an SR for the CE to replace all spare drives which are pending replacement.

There is an AutoPse script that runs on the service processor, whenever a drive fails the AutoPSE script collects the RMA information for the drive ie serial number, part number etc. This script check is deffered disk service is enabled and if all drives have covering spares.