Disk Tier High RAID 10-2 has substituted page allocations with different Disk Tier and/or RAID Level

Staybox,

To start I would be curious if you are running on the latest supported version of SCOS, primarily if you are using SCOS 7.5.1 or later?

If so then would you pull a support bundle and upload it tot he Service Request, as explained here.  I will private message you the SR# to use to attach the logs to. 

Let me know what you see.

Hello,

Version: 7.4.21.4

Hello,

can you update to the last SCOS version and check if problem is the same?

Thanks

Hello!

I don't have access to new firmware. Therefore, unfortunately, it is unlikely that I will be able to update to a newer version.

Hi Chris,

I see the exact same warning on my SC4020. I don't get what the warning is about in the first place. There's plenty of space on both tiers. The source name is "Assigned - Redundant - 512 KB". Status says "Degraded", which doesn't sound good. 

Running on 7.5.10.12, I think it's the latest version. 

Any idea what this warning is about, and how to mitigate it? 

Best regards,

CG

Cosminidis,

This can be caused by a few different things, for example

1. Insufficient Free Space in the target tier or RAID level.
2. Tier or RAID Constraints due to disk health, rebuilds, or provisioning limits.
3. SCOS Version Behavior – Older versions (e.g., SCOS 7.4.x) may be more sensitive to allocation logic.
4. Temporary Performance Optimization – The system may reallocate to maintain performance or redundance

What I suggest you start with is to check available space in the affected tier using Storage Center Manager or DSM. I would also recommend that you also review tier policies and ensure that the volume or folder has correct tier affinity and RAID preferences. Laslt,y I would upgrade SCOS to 7.5.1 or later, as previously stated.

Let me know if this helps and what you see. 

Hi Chris,

SCOS is on version 7.5.10.12. 

Space is ok, I'm using ~50% of the total available space:

Profiles look good as well, and there's plenty of space:

However, in the Storage Types tab I see indeed that Tier 1 is full, probably waiting for the data migration during the night. I'm not sure how these values are calculated, as I have 1.09TB of space on the write intensive SSDs, and the unit complains that it's full at 344GB. Why isn't it using the whole allocated space?

Hi,

It might be page pool that being using up the space, usually it does. Try to check under Storage Usage tab or Disk tab to check if the page pool size is taking up space. 

If the page pool is filling up, I would suggest not deleting them if there is uncertainty, and contact support to remote into the storage to confirm the page pool can be deleted. 

Hi Joey,

Could you please detail where to look for the page pool usage? I cannot find that info anywhere (not in the web interface, nor in the fat client). 

The pressure report shows ok, but I don't really understand the differences between "Disk Space Available", "Disk Space Allocated", "Disk Allocated", "Disk Used", "Volume Allocated" and "Volume Used". Basically I'm limited to 344.90 GB, although there's enough space on this tier (RAID 10 single redundancy on 6 x 200GB, which makes up for ~600GB usable space).

Best regards,

CG

You can view the page pool usage by following these steps:

Log in to the Storage Center GUI using a web browser.
Once logged in, navigate to the Performance tab.

Select System Resource Metrics from the drop-down menu.

In the System Resource Metrics section, click on the Memory tab.

The page pool usage will be displayed in the Page Pool section, which includes metrics such as:

Page Pool Usage : The current percentage of page pool usage.
Page Pool Available : The amount of available page pool memory.
Page Pool Total : The total amount of page pool memory.

Now as far as the definitions, they are as follows'

Disk Space Available : The total amount of free space available on the physical disks in the storage system.

Disk Space Allocated : The total amount of space allocated to the storage system's internal data structures, such as the page pool, metadata, and other system overhead.

Disk Used : The total amount of space used by the storage system, including allocated space, data, and other system overhead.

Disk Allocated : This metric is similar to Disk Space Allocated , but it specifically refers to the space allocated for data storage, excluding system overhead.

Volume Allocated : The total amount of space allocated to a specific volume or storage container.

Volume Used : The actual amount of space used by the data stored in a specific volume or storage container.

Thank you Chris. I don't see System Resources Metrics anywhere in the interface (printscreen below). I've looked in the fat client (Dell Storage Manager Client) as well. I've checked everywhere, in Most Active Reports, all buttons in Performance tab. 

The system is a SC4020, running on the latest SCOS (7.5.10.12)

Best regards,

CG

Sorry about that I was thinking of another tool. Would you do me a favor and confirm how many disks are in the raid 10, and what redundancy level do you have set? I ask as it may be that it has 4 drives with dual redundancy, so the data is written 3 times. 

Also, I found another posting that discusses this as well. 

I think that we are likely going to need you to call in to support, as it will likely require reviewing the logs, and working directly with you to resolve the issue.

Sure, there are 6 x 200GB SSDs configured in RAID 10 with single redundancy. That should account for ~600GB of usable space. I don't understand why there is such a big difference between disk allocated and volume allocated, it should be more or less the same value. 

The unit is not covered by warranty anymore, but I can manage to get the logs if you point me to the right direction. I have access to the CLI over serial as well if needed. 

Best regards,

CG

Hi,

For disk allocation refers to the amount of physical disk space that has been reserved or committed by the system for use. For volume allocation refers to the logical space assigned to volumes (LUNs) presented to hosts.

The available disk allocated seems to be ~600GB but the volume allocation is only ~300GB.

Is there a way to force the volume allocation to increase closer to the ~600GB mark?