7200/7400 adding disks

[Josh26]

Our HP reps made it out to be as simple as, "If you need more space, add the drives and you're done.". .

Then maybe you should ask why they don't sell additional drives without a compulsory installation service.

[aperia]

Thanks, afidel, that makes sense. I was told that when we order new drives/cages if we did not have DO licensing we would have to run tunesys. If our DO licensing was applied it will take care of the new spindles and the manual tunesys would not be needed. I will run this by our rep and see what he comes back with. We have DO for all drives and all CPGs span all spindles.

[aperia]

In case anyone else has questions about adding disks, below are all the steps we walked through for a successful addition of 12 drives. We have a 7200, 2 cages and went from 36 900GB 10K SAS drives to a full 48 with DO licensing for 48 disks, no AO.

1. Apply DO license key (if applicable). If no DO, you will need to build new CPGs and migrate existing vvols to them once complete.
2. Verify all mags are licensed via the CLI command showlicense.
3. Plug in all disks. Each new disk will go through 3 phases visible in the management console under Systems -> Physical Disks -> Physical Disks tab: Missing, then New and finally Normal. This process took about 30 to 40 seconds for each disk on my system.
4. Run admithw from the CLI. Optionally run admithw -checkonly to do a dry run. admithw will ensure the new disks are available to the system and check for any issues that may exist on your system.
5. Due to a bug in v3.1.2 and below, you must change all CPG's Device RPM settings from what you have now to its other option. For instance, one of my CPGs was set to 10K and the other to Default. I changed each to its other option available in the drop down menu, i.e, I changed one from Default to 10K and the other from 10K to Default. This bug is fixed in the currently non-public release v3.1.3 firmware. I saw no noticeable impact from this modification.
6. Run tunesys from the CLI to begin balancing chunklets.

You can monitor the status of tunesys via the management console. Go to Tasks & Schedules, click the Tasks tab at the top and you will see the System Tuning percentage progress. One at a time you will see multiple Move Regions processes, each taking different amounts of time to complete. I'm at 55% after 3 days.

[Cleanur]

Step 1 is a little confusing.

You don't actually need to license DO in order to re-balance the array after adding new drives, nor should you need to create new CPG's to migrate volume to.

DO licensing allows you to tune individual volumes to new CPG's with differing properties e.g Disk Class, RPM, Raid Type, Stripe Size etc so it's a more granular data mobility tool than tunesys which is system wide.

Tunesys is basically a free subset of the above DO functionality which allows automated re-balancing of data across all drives in the array, however it lacks the above granularity of control that DO provides for individual volumes.

So whether or not you have DO licensing, you simply need to run Tunesys after adding new drives and you're done, no need to create new CPGs as the new drives will automatically be added to the existing CPG's (assuming you didn't set a custom filter).

Hope this makes sense.

[aperia]

Step 1 is a little confusing.

You don't actually need to license DO in order to re-balance the array after adding new drives, nor should you need to create new CPG's to migrate volume to.

DO licensing allows you to tune individual volumes to new CPG's with differing properties e.g Disk Class, RPM, Raid Type, Stripe Size etc so it's a more granular data mobility tool than tunesys which is system wide.

Tunesys is basically a free subset of the above DO functionality which allows automated re-balancing of data across all drives in the array, however it lacks the above granularity of control that DO provides for individual volumes.

So whether or not you have DO licensing, you simply need to run Tunesys after adding new drives and you're done, no need to create new CPGs as the new drives will automatically be added to the existing CPG's (assuming you didn't set a custom filter).

Hope this makes sense.

Unless I am misunderstanding the explanations I was given and HP's own description of DO here, http://www8.hp.com/us/en/products/stora ... b=features, DO is needed or at least beneficial to re-balancing existing chunklets on CPGs. Tunesys is part of this, but DO is needed to properly re-balance: "Drives large scale performance optimizations with one-button system rebalance after adding new resources to the system...".

When you add new disks to a system with existing CPGs, from all I've read and what HP senior techs explained to me, DO must be configured before adding them or existing CPGs will continue to write chunklets only to the original drives they were created with, even after tunesys. Without DO, the only way to mitigate this behavior is to create a new CPG which spans all disks and migrate vvols from the original CPGs to it. This info is straight from multiple engineers at HP as well as our HP solutions architect.

[afidel]

I don't believe that's correct, the entire point of tunesys is to redistribute data across all spindles in a tier when you add additional capacity, if existing CPG's weren't relaid out then tunesys would be rather pointless. The difference is that DO allows you to move just one vvol at a time (as an example to move a database vvol from RAID5 to RAID10 if it's not performing satisfactorily)

[Cleanur]

Correct Tunesys is a subset of DO used for whole system tuning, think leveling on HP EVA but manually initiated. Prior to 3.1.1 tunesys did not exist and you needed to have DO licensed to re-balance the array. Since 3.1.1 tunesys functionality is included in the base O/S.

Tunesys will take the data on existing drives pick it up and spread it evenly across old and new drives as they are added to the CPG. All net new writes will then be spread across the new and old disks evenly within the CPG so no need to DO individual volumes.

However DO provides much greater flexibility since tuning can be on a per volume level; rather than system wide. E.g didn't mean to put that on SSD then move it to FC, don't want cage prefer mag, don't like that stripe size, Raid 1 is not beneficial to that volume then just re-tune to Raid 5. raid 6, back to raid 1 etc etc.

DO provides huge flexibility, whereas tunesys today simply looks to balance capacity based on CPG properties across all nodes and all disks of a given class within the array, which although relatively simple is extremely useful and still fairly unique.