XIV Capacity Upgrade - as easy as 1, 2.. done
anthonyv 2000004B9K Comments (2) Visits (6424)
So I had the pleasure last night of observing a capacity upgrade on a client's XIV (so yes this is all real world).
The client in question had an 11 module XIV with 1 TB drives. This meant they had 54,649 GB of useable capacity ( approx 54TB ).
They client had ordered one new XIV module as an incremental capacity upgrade
All hardware upgrades are performed by IBM, so the upgrade work was all done by an IBM System Service Representative (SSR)
Task one for the IBM SSR was to remove the blanking plate at the front of the machine and slide the new module into place.
The module was then secured into place with its two captive screws (the only time a tool was needed).
The next task was delegated to me.... which was attaching the sticker (decal) which showed the relevant module number.
In our case the new module was module number 12.
Here you can see the new module with all the available decals (I think I did a good job).
Note the cables have not been plugged in yet.
Because the XIV is pre-cabled, all that the IBM Service Representative needed to do was plug the ethernet and power cables into the new module.
You can see all the cables plugged in and the lights are now on:
Once this was done, the module booted up and became available in the XIV GUI.
The IBM Service Representative needed to issue two commands to complete the upgrade (literally two mouse clicks in the GUI).
The first command, called an equip, introduces the module to the XIV and places it into the Ready state, as shown below:
The second command issued by the IBM SSR starts a process known as re-distrubution.
At bottom right the message changed from 'Full redundancy' to 'Redistributing'.
What does this mean?
It means the XIV is automatically spreading existing data across the new disks to load level the amount of data on each disk.
The machine will then be in a state of workload balance without any user intervention or host interruption.
This process is done with low priority, meaning the predicted end time kept jumping around as host I/O workload rose and fell.
To monitor the process, we used the XCLI command, monitor_redist as shown below:
The process actually ran all night, moving 8TB of data around the machine to ensure the most ideal data layout.
In the morning the redistribution had finished.
The machine now reported 'Full redundancy' and the useable capacity had risen from 54649 GB to 61744 GB
(the increase varies according to which module is being added).
Two tasks remained for the customer to complete:
1) Increase the size of the relevant storage pool(s) - takes a couple of mouse clicks, perhaps 20 seconds work.
2) Creates new volumes in those pools. Which again, takes just seconds to perform.
The XIV has two concepts when it comes to space:
Hard limit --> How much useable capacity you ACTUALLY have
Soft limit --> How much space you can allocate to volumes.
The ability to set the Soft Limit above the Hard Limit means you can over allocate the hard capacity (if you so choose!).
In the screen captures, the Hard and Soft Limits went up because the amount of useable capacity went up.
So to sum up..... to increase the capacity of the XIV while maintaining perfect load balance, the IBM Service representative performed about
2-3 minutes of physical work and then used two mouse clicks. Redistribution began and ran as a background task.
In the morning the client then increased the size of a storage pool (two mouse clicks) and the space was now ready for new volumes.
Easy as..... XIV.