Why does a LUN fail to be created because of insufficient RAID capacity, whereas the RAID capacity is actually sufficient?

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This occurs when RAID capacity is not refreshed in a timely manner due to busy services. In this case, the interface still displays the RAID capacity that is seemingly not used for creating a LUN. Therefore, when another LUN that requires a larger capacity than the remaining capacity of the RAID group is to be created, a message is displayed, stating that available capacity is insufficient.

To avoid this problem, we recommend that you wait after creating a LUN until the system automatically refreshes itself. After the refresh, you can proceed to create another LUN using the remaining capacity of the RAID capacity.

Other related questions:
Adding a disk to a RAID array
You can add a disk to a RAID array as follows: 1. If the LSISAS2208 or LSISAS3108 RAID controller card is used, you can add a new disk to a RAID array online. For details about how to expand the virtual disk (VD) capacity online, see HUAWEI Server RAID Controller Card User Guide 09. 2. If the LSISAS2308 or LSISAS3008 RAID controller card is used, you cannot add a disk to a RAID array through online capacity expansion and cannot expand the VD capacity online. 3. If softRAID is used, you cannot add a disk to a RAID array online or expand the VD capacity online.

Method used to calculate RAID capacity
If the number of RAID member disks is N (excluding hot spare disks), available capacity of RAID 0 = N x disk capacity. Available capacity of RAID 1 = N x Disk capacity/Number of mirror groups Available capacity of RAID 3 = (N-1) x Disk capacity Available capacity of RAID 5 = (N-1) x Disk capacity Available capacity of RAID 6 = (N-2) x Disk capacity Available capacity of RAID 10 = N x Disk capacity/Number of mirror groups Available capacity of RAID 50 = (N-2) x Disk capacity

Method of calculating the available capacity before configuring RAID
1. You can view the available capacity during RAID array configuration. 2. You can also estimate the ? RAID 0: 100% ? RAID 1: 50% ? RAID 5: (N-1)/N ? RAID 6: (N-2)/N ? RAID 10: 50% ? RAID 1E: (N+1)/2N ? RAID 50: (N-M)/N ? RAID 60: (N-M*2)/N N indicates the number of member hard disks in a RAID array. M indicates the number of sub-groups of a RAID array. For example, if three 300 GB disks are used to create a RAID 5 array, Disk usage rate: (3-1)/3 = 2/3 Available capacity of the RAID 5 array: 3 x 300 x 2/3 = 600 GB

Whether a RAID group can be created when the capacity of member disks is different
Whether a RAID group can be created when the capacity of member disks is different: Yes. Total capacity of a RAID group = Minimum capacity of member disks in a RAID group x Quantity of member disks Therefore, if disks with different capacity are selected as member disks in a RAID group, the storage space of member disks may be wasted. It is recommended that disks with the same capacity be selected to create a RAID group.

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