johnsmith1971
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Unisphere on VMAX - Capacities

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Hi,

I'm having a bit of trouble understanding certain things on Unisphere.

I have a VMAX 20K where LUNs are configured as Thin.

Now i want to figure out how much actual capacity im consuming from my VMAX. I have 3 tiers (SSD, FC, SATA) configued with FAST VP.

I think if i can figure out the exact meanings of the below properties, i can have a clear idea:

- Total Capacity

- Free Capacity

- % Allocated

- Maximum Subscription

- % Subscription

- Enabled Capacity

- Allocated Capacity

As you can see, these are ALOT of capacity parameters to grasp,but what i am interested in is:

- Total Physical Usable Capacity

- Total Physical Free Capacity

- Total THIN Free Capacity

- Total Physical Used Capacity

- Total ALLOCATED capacity (presented to hosts.. what the hosts can see)

I hope im making sense here. Appreciate all the help!

JS

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sauravrohilla
3 Argentium

Re: Unisphere on VMAX - Capacities

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Total Capacity = Sum of capacities of Data Devices (enabled or disabled) in the pool (which is the total physical capacity of the pool) - Yes (some customers would have a dedicated disk group for thick boot luns but generally not considered in capacity planning)

Free Capacity = Out of all the "enabled" Data Devices, how much is free? or our of ALL the Data Devices (enabled and disabled), how much is free - Free capacity should be the total free capacity on enabled & disabled data devs.

% Subscription = Couldn't figure it out - Are you talking about the max subscription %? In general, subscription % of the tdev means how much you have used from the bound pool?

Enabled Capacity = We can enable or disable data devices in a Thin Pool. So the Enabled Capacity is the sum of ALL enabled data devices. - Yes

Allocated Capacity = Out of the "Enabled Capacity", how much are bound to Thin Devices - It is the amount of space you have allocated for tdev in a pool using the allocate command. If allocated to 100%, it means you have blocked the space in pool equal to your tdev size.

% Allocated = (Allocated Capacity / Enabled Capacity) x 100 - please confirm? I guess

Apart from usable capacity and allocated capacity, you should look at the actual written capacity also. total written should not be getting close to usuable capacity and to avoid oversubscription, you can set the max oversubscription to 100%.

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sauravrohilla
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Re: Unisphere on VMAX - Capacities

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yes you are right. If you understand the above parameters, you can find out the actual usage. As a starter, you can add up allocated capacity of all pools to get the total allocated space to your hosts and sum of written capacity will tell you the actual used capacity.

Below is the sample data i have captured from SMC. if you sum up the total written of all devices, you will get the actual written capacity of VMAX.

DevDataStore NameCap (MB)Total Subscribed %Pool Alloc Cap (MB)Pool Allocated %Total Written Cap (MB)Total Written %Status
01D6XXX-mc-rls00240960030040959100Bound
01D7XXX-mc-rls004409600480140959100Bound
01D8XXX-mc-dss002197001023129260775130538Bound
01E0XXX-mc-rls00610250323311023100Bound
01E1XXX-mc-rls005102400155065102399100Bound

regards,

Saurabh

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johnsmith1971
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Re: Unisphere on VMAX - Capacities

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Thank you Saurabh.

Would it be possible for you to provide me with a brief explanation of the following just to clear my confusion please:

- Total Capacity

- Free Capacity

- % Allocated

- Maximum Subscription

- % Subscription

- Enabled Capacity

- Allocated Capacity

Thanks

JS

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sauravrohilla
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Re: Unisphere on VMAX - Capacities

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johnsmith1971
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Re: Unisphere on VMAX - Capacities

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Thank you Saurabh. I dont know if this is confusing in general or if its just confusing me...

I could figure out the following:

Total Capacity = Sum of capacities of Data Devices (enabled or disabled) in the pool (which is the total physical capacity of the pool) - please confirm?

Free Capacity = Out of all the "enabled" Data Devices, how much is free? or our of ALL the Data Devices (enabled and disabled), how much is free - please confirm?

% Subscription = Couldn't figure it out - any ideas?

Enabled Capacity = We can enable or disable data devices in a Thin Pool. So the Enabled Capacity is the sum of ALL enabled data devices. - please confirm?

Allocated Capacity = Out of the "Enabled Capacity", how much are bound to Thin Devices - please confirm?

% Allocated = (Allocated Capacity / Enabled Capacity) x 100 - please confirm?


My main concern is, i am planning for storage expansion and i want to understand how much my TOTAL USABLE capacity is and how much is actually allocated to servers. I dont want to have my capacity "oversubscribed" for now.


Thanks

JS

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sauravrohilla
3 Argentium

Re: Unisphere on VMAX - Capacities

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Total Capacity = Sum of capacities of Data Devices (enabled or disabled) in the pool (which is the total physical capacity of the pool) - Yes (some customers would have a dedicated disk group for thick boot luns but generally not considered in capacity planning)

Free Capacity = Out of all the "enabled" Data Devices, how much is free? or our of ALL the Data Devices (enabled and disabled), how much is free - Free capacity should be the total free capacity on enabled & disabled data devs.

% Subscription = Couldn't figure it out - Are you talking about the max subscription %? In general, subscription % of the tdev means how much you have used from the bound pool?

Enabled Capacity = We can enable or disable data devices in a Thin Pool. So the Enabled Capacity is the sum of ALL enabled data devices. - Yes

Allocated Capacity = Out of the "Enabled Capacity", how much are bound to Thin Devices - It is the amount of space you have allocated for tdev in a pool using the allocate command. If allocated to 100%, it means you have blocked the space in pool equal to your tdev size.

% Allocated = (Allocated Capacity / Enabled Capacity) x 100 - please confirm? I guess

Apart from usable capacity and allocated capacity, you should look at the actual written capacity also. total written should not be getting close to usuable capacity and to avoid oversubscription, you can set the max oversubscription to 100%.

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B2seb2ll
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Re: Unisphere on VMAX - Capacities

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"Allocated Capacity = Out of the "Enabled Capacity", how much are bound to Thin Devices - It is the amount of space you have allocated for tdev in a pool using the allocate command. If allocated to 100%, it means you have blocked the space in pool equal to your tdev size."


That can't possibly be. We are using Thin Pools and Fast VP and I am unable to bind any more volumes to a pool that is reported as using only 52% "Allocated Capacity". I would believe you if you said this is the amount of physical space consumed out of the DATA Volumes that make up the pool. My claim is further supported by observing that each DATA Volume is about 52% consumed in the Related Objects link in the Pool details.

That being said, is there truely a way to find out how much Capacity has been Allocated? I look at it like booking a flight. I have a 100 seats on the plane but I can over book it. Over booking it is fine as long as I don't have 101 or more people show up to fill the seats. It appears to me that I have no idea of knowing how many tickets I've sold for the flight though.



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KW160
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Re: Unisphere on VMAX - Capacities

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Your pool has a subscription limit set most likely. The subscription limit applies only to the bound capacity and has no bearing on the actual allocated capacity. If you want to bind more capacity to this pool you can raise that subscription limit higher. (It is probably set to 100% right now).

For a FAST VP environment the bound capacity really has no bearing on the allocated capacity. Although a single TDEV will only be bound to one pool (usually FC) the capacity can come from any pool in the FAST policy.

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B2seb2ll
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Re: Unisphere on VMAX - Capacities

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Yes for certain the subscription rate is set to 100%, because we are unable to do anything quickly (government) to address capacity needs if we oversubscribe the pool. According to the Unisphere console it reports me having consumed 52% of the allocated capacity. When in fact it is somewhere just shy of 100% since I am unable to bind any more volumes to that Pool. How do I find out what the real allocated capacity is?

Going back to my plane example, I have booked 100% of the seats for the pool in question, though Unisphere says I have only booked 52%. I believe that the 52% actually refers to having people sitting in 52% of the seats so if I wanted to overbook the flight I have 48% of the plane to work with since almost half of the consumable capacity hasn't been written to. From what I can tell there is no way to find out how many plane tickets I have truly sold (allocated capacity).

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KW160
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Re: Unisphere on VMAX - Capacities

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Bound/subscribed capacity == the sum of all the TDEVs bound to that pool. (Total fully inflated size, not thin)

Allocated capacity == the sum of all the actual data written to that specific pool.

Your allocated capacity is, as you stated, 52%. Your bound capacity is likely 99 or 100% since you say that you cannot bind any more. The problem with your plane example above is that the array is made up of multiple pools.You are only considering one of them in your example. Each pool has both a bound (subscribed) number and an allocated (written to) number.

Essentially what's happened here is that you've likely bound everything to FC, while FAST VP has then gone ahead and moved data around into other pools. So you've 100% bound your FC pool, but now some of that data is in other pools. Bound/subscribed does NOT take FAST VP into account. It is quite simply the summation of all bound TDEVs to that specific pool.

For example, you might have a 100GB TDEV bound to FC, but FAST VP has gone ahead and moved all that data into flash. In this example your 100GB TDEV is counting toward the subscribed % for FC but accounting for the allocated % in flash.

In your instance you should be looking at the capacity of the entire array when setting subscription limits. Either that, or start binding to other pools that have not yet met their subscription limit.

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