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FAQs

Frequently asked questions...

  • What is a hot spare drive?
    Hot spares act as standby drives in RAID 1, RAID 5, or RAID 6 volume groups. They are fully functional drives that contain no data. If a drive fails in the volume group, the controller automatically reconstructs data from the failed drive to a hot spare.
  • What is a volume group?
    A volume group is a container for volumes with shared characteristics. A volume group has a defined capacity and RAID level. You can use a volume group to create one or more volumes accessible to a host. (You create volumes from either a volume group or a pool.)
  • What is a pool?
    A pool is a set of drives that is logically grouped. You can use a pool to create one or more volumes accessible to a host. (You create volumes from either a pool or a volume group.)
  • What is a volume?
    A volume is a container in which applications, databases, and file systems store data. It is the logical component created for the host to access storage on the storage array.
  • What is reserved capacity?
    Reserved capacity is the physically allocated capacity that stores data for copy service objects such as snapshot images, consistency group member volumes, and mirrored pair volumes.
  • What is FDE/FIPS security?
    FDE/FIPS security refers to secure-capable drives that encrypt data during writes and decrypt data during reads using a unique encryption key. These secure-capable drives prevent unauthorized access to the data on a drive that is physically removed from the storage array.
  • What is redundancy check?
    A redundancy check determines whether the data on a volume in a pool or volume group is consistent. Redundancy data is used to quickly reconstruct information on a replacement drive if one of the drives in the pool or volume group fails.
  • What are the differences between pools and volume groups?
    A pool is similar to a volume group, with the following differences.
  • Why would I want to manually configure a pool?
    The following examples describe why you would want to manually configure a pool.
  • Why are capacity alerts important?
    Capacity alerts indicate when to add drives to a pool. A pool needs sufficient free capacity to successfully perform storage array operations. You can prevent interruptions to these operations by configuring System Manager to send alerts when the free capacity of a pool reaches or exceeds a specified percentage.
  • Why can't I increase my preservation capacity?
    If you have created volumes on all available usable capacity, you might not be able to increase preservation capacity.
  • Is there a limit on the number of drives I can remove from a pool?
    System Manager sets limits for how many drives you can remove from a pool.
  • What media types are supported for a drive?
    The following media types are supported: Hard Disk Drive (HDD) and Solid State Disk (SSD).
  • Why are some drives not showing up?
    In the Add Capacity dialog, not all drives are available for adding capacity to an existing pool or volume group.
  • What is shelf loss protection and drawer loss protection?
    Shelf loss protection and drawer loss protection are attributes of pools and volume groups that allow you to maintain data access in the event of a single shelf or drawer failure.
  • How do I maintain shelf/drawer loss protection?
    To maintain shelf/drawer loss protection for a pool or volume group, use the criteria specified in the following table.
  • What RAID level is best for my application?
    To maximize the performance of a volume group, you must select the appropriate RAID level. You can determine the appropriate RAID level by knowing the read and write percentages for the applications that are accessing the volume group. Use the Performance page to obtain these percentages.
  • What is Data Assurance?
    Data Assurance (DA) checks for and corrects errors that might occur as data is communicated between the Controllers and Drives on a Storage Array. DA capabilities are presented at the pool and volume group level in System Manager .
  • What is secure-capable (Drive Security)?
    Drive Security is a feature that prevents unauthorized access to data on secure-enabled drives when removed from the storage array. These drives can be either Full Disk Encryption (FDE) drives or Federal Information Processing Standard (FIPS) drives.
  • What do I need to know about increasing reserved capacity?
    Typically, you should increase capacity when you receive a warning that the reserved capacity is in danger of becoming full. You can increase reserved capacity only in increments of 4 GiB.
  • Why can't I choose another amount to decrease by?
    You can decrease reserved capacity only by the amount you used to increase it. Reserved capacity for member volumes can be removed only in the reverse order they were added.
  • Why would I change this percentage?
    Reserved capacity is typically 40 percent of the base volume for snapshot operations and 20 percent of the base volume for asynchronous mirroring operations. Usually this capacity is sufficient. The capacity needed varies, depending on the frequency and size of I/O writes to the base volume and how long you intend to use the storage object's copy service operation.
  • Why do I need reserved capacity for each member volume?
    Each member volume in a snapshot consistency group must have its own reserved capacity to save any modifications made by the host application to the base volume without affecting the referenced consistency group snapshot image. Reserved capacity provides the host application with write access to a copy of the data contained in the member volume that is designated as read-write.
  • Why do I see more than one reserved capacity candidate?
    You see more than one reserved capacity candidate when System Manager detects more than one volume in a pool or volume group that meets the capacity percentage amount you selected for the storage object.
  • How do I view and interpret all SSD Cache statistics?
    You can view nominal statistics and detailed statistics for SSD Cache. Nominal statistics are a subset of the detailed statistics. The detailed statistics can be viewed only when you export all SSD statistics to a .csv file. As you review and interpret the statistics, keep in mind that some interpretations are derived by looking at a combination of statistics.