Configuring Storage Pools

Configuring Storage Pools

Understanding Storage Pools

Storage Pools are virtual entities that manage storage provisioning from the aggregated capacity of one or more RAID Groups pooled into a single construct with some QoS attributes.

Volumes are thinly provisioned, allocating capacity from the Pool only when needed. The Pool has an underlying block virtualization layer which maps virtual address space to physically allocated Pool space and manages sharing of Pool physical chunks between Volumes, Snapshots and Clones.

Snapshots and Clones consume zero capacity when they are created because they share the same data chunks as the originating Volume. Anytime you actually modify the data in the Volume, or in one of the Clones, the data chunk is copied-on-write (COW) from the source in order to apply the new data write to a new pool region without affecting the data set of any other objects that share the same data chunk.

The Pool’s attributes define the way Volumes, Snapshots and Clones are provisioned.


imageAFA Understanding Pool’s Capacity

The introduction of data reduction makes the pool capacity management more complex. Data reduction efficiency depends on the nature of the data, therefore it harder to predict the drives capacity needed for each workload.

Capacity metrics to consider:

Physical View

Raw Capacity - Sum of all drives’ capacities in the Pool

Usable Capacity - Total capacity of all RAID groups in the Pool

Note

the system keeps about 0.5% of each RAID Group capacity as its internal spare

Used by Volumes - Capacity used to store the Volumes data

Used by metadata - Capacity used to store the Pool’s metadata

Used by data copies: - Capacity used to store the snapshots and clones

Used Capacity - The total size of all data written in the Pool

Used Capacity = Used by Volumes + Used by metadatra + Used by data copies

Free Capacity - Available Capacity in the Pool that can be used for new Data and Metadata writes

Free Capacity = Usable Capacity – Used Capacity

%Full = “Used Capacity” / “Usable Capacity”

Note

Capacity alerts are based on Free Capacity

Virtual View

Provisioned Capacity - Sum of Pool’s Volumes and Clones capacities as seen by the hosts

Allocated Capacity - Pool’s allocated address space of all Volumes, Snapshots and Clones

Allocation Limit - Max Capacity of the Pool’s address space. Depends on the pool type. See

Free Address Space = Allocation Limit – Allocated Capacity

Note

Address Space alerts are based on Free Address Space

Effective Capacity - Amount of data written in the pool by all volumes and can be accessed by hosts. Not including space taken by snapshots

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Data Reduction Saving

Thin Provision Ratio = Provisioned Capacity / Effective Capacity

Data Reduction Ratio = Effective Capacity / Used by Volumes

Data Reduction Saving = Effective Capacity - Used by Volumes

Data Reduction Percentage = 1- (1 / Data Reduction Ratio)

e.g.

Data reduction ratio 2:1 , Data Reduction Percentage 50%

Data reduction ratio 5:1 , Data Reduction Percentage 80%

Data reduction ratio 20:1 , Data Reduction Percentage 95%


Pool capacity Monitoring

The All Flash VPSA Dashboard show the capacity consumption and data reduction saving

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The upper bar shows the current capacity provisioned to the hosts by all pools vs. the effective capacity written by the hosts vs. the physical space needed to store the data.

The lower chart shows trend of time of the physical capacity used and available.

The Pools table shows 2 bars.

The physical capacity bar shows the usable vs. used capacities.

The virtual capacity bar shows the allocated capacity vs. the allocation limit.

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Creating and Managing Pools


Creating a Pool

Note

By dafault when a a new VPSA is created, a default pool is automatically created for each type of drives selected for this VPSA.

If the default pool does not meet the needs, you can delete it and follow the process described here to create your own pools.

To create a new Storage Pool press either the Create button on the Pools page or the Create Pool button on the RAID Groups page. There are 2 methonds to create a pool.

  1. Create a Pool from RAID Groups
  2. Create a Pool from drives, and the let the system automatically create the needed RAID Groups.

You can toggle between the two by clicking Use Drive Selection / Use RAID Group Selection at the lower left corner of the dialog

To create a Pool from RAID Groups, you will see the following dialog:

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Select the Pool attributes:

  • Display Name – You can modify this anytime later.

  • RAID Group(s) selection – Check the box(es) of one or more RAID Groups from which protected storage capacity will be allocated for this Pool.

  • Capacity – The Pool’s physical capacity shown in GB. By default the capacity is the aggregated capacities of all the selected RAID Groups, but you do not have to allocate full RAID Groups. If you define a capacity smaller than is available in the selected RAID groups the capacity will be evenly distributed between the RAID Groups.

    Note

    The actual usable capacity of the Pools is a little less than the requested size, as the system reserves some space for the Pool’s metadata (typically up to 100GB).

  • Type – The VPSA supports Transactional, Repository and Archive Pool types. These Pool types use different chunk sizes for the mapping of virtual LBAs to Physical Drive addresses. The following table describes the tradeoffs for each type and the recommended use cases:

imageSA Storage Array Pool types:

  Transactional Pool Repository Pool Archive Pool
Chunk size 256KB 1MB 2MB
Pros
  • Faster COW operation
  • Space efficiency on Random writes to Snapshots
  • Smaller metadata size
  • Sequential workload performance is similar to transactional
  • Allows large pools
  • Sequential workload performance is the same
Cons Increased metadata size
  • Slower COW operation
  • Less space efficient
  • Slower with frequent data modifications
  • Limited Snapshots frequncy (1 hour min)
Use Case Transactional Workload with Snapshots
  • Repository type workload.
  • Large Pools
  • Many snapshots to keep
  • Relatively static data
  • Archive type workloads
  • very large pools/volume (> 100TB)
Limit Transactional Pools have a maximum size of 20TB
  • Repository Pools have a maximum size of 100TB
  • Archive Pools have a maximum size of 200TB

imageAFA All Flash Array Pool types:

  Transactional Pool Repository Pool Archive Pool
Thin Provision Chunk size 512KB 1MB 2MB
Deduplication Chunk size 8KB 16KB 32KB
Pros
  • Faster COW operation
  • Space efficiency on Random writes to Snapshots
  • Better Deduplication
  • Smaller metadata size
  • Sequential workload performance is similar to transactional
  • Allows large pools
  • Better sequential workload throughput
  • Better Compression ratio
Cons
  • Increased metadata size
  • Lower throughput
  • Slower COW operation
  • Less space efficient
  • Slower with frequent data modifications
  • Limited Snapshots frequncy (1 hour min)
Use Case
  • Transactional Workload with Snapshots
  • High IOPS
  • Database (OLTP)
  • Analytics
  • High Troughput
  • General Purpose
  • File System
  • Relatively static data
  • Archive type workloads
  • Sequntial workloads like Video Streaming
  • Very large pools/volumes (> 200TB)
Limit
  • Transactional Pools have a maximum size of 50TB
  • Repository Pools have a maximum size of 100TB
  • Archive Pools have a maximum size of 200TB

In case there are number of pools in a given VPSA, there is a limit to aggragated total size of all pools. The following table lists the capacity limits of all pools per each VPSA All Flash engine:

Pool Type Engine F800 F1200 F2400 F3600 F4800
Transactional 20 40 60 80 100
Repository 40 60 100 160 200
Archival 60 100 160 200 250

  • Cached – Check this box to use SSD to Cache Server’s reads and writes.
    • All Pools that are marked as “Cached” share the VPSA Cache.
    • Flash cache usually improves the performance of volumes based on HDD’s pools. However it depends on the specific workload and the size of the cache vs. the size of the active data set.
    • If the Pool consists of SSD drives this option will be disabled.
  • Striped – This check box is enabled only when you select two or more RAID Groups. Striping over RAID-1 or RAID-6 creates RAID-10 or RAID-60 configurations respectively. Use striping to improve performance of random workloads since the IOs will be distributed and all drives will share the workload.

imageAFA

All Flash Array pools are always striped, and this checkpoint is hidden.

To create a Pool from Drives, you will see the following dialog:

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The parameters are same as above. Just Check the box(es) of drives that will be allocated for this Pool.


Expanding Pool Capacity

To Expand the Pool press the Expand button on the Pools page.

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You can use capacity from any RAID Group to expand a Pool. If the RAID Group from which the new capacity is added doesn’t match the protection type or drive type of the existing capacity you’ll see a warning message pop up asking you to confirm the mismatch. Keep in mind that continuing with the mismatched types may impact the pool performance and protection QoS.


imageAFA Shrinking Pool Capacity

If the pool capacity is not fully used, you can shrink it’s size by removing RAID Group (one at a time) from the Pool. The VPSA will evacuate the selected RAID Group, and will return the RAID Group to the VPSA for another use. To Shrink the Pool press the Shrink button on the Pools page.

imageShrinkPool

Select the RAID Group to remove from the Pool. Check the physical size expected after the shrinking operation is completed, and press Shrink The operation might take a while, depending on the amount of data to be copied to other drives. The system will generate Event once done.

Note

Pool shrink is only supported in All Flash VPSAs.


imageSA

It is possible to enable Caching on non-cached Pools.

One use case for leveraging this capability is to enable caching only after the initial copy of the data into the VPSA. The initial copy typically generates a sequential write IO workload, where non-cached Pools are most efficient. Once the initial copy is completed enable caching on the Pool if you expect a more random type of IO workload.


imageSA Disabling SSD cache on a pool

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By default every pool is cached by the VPSA’s SSD cache, but it is also possible to disable caching on cached Pools which will remove this feature. The Enable Cache/Disable Cache buttons toggle depending on the current caching state of the Pool.


Viewing Pool properties

The Pools details are shown in the following South Panel tabs:

Properties


imageSA Each Pool of Storage Array includes the following properties:

Property Description
ID An internally assigned unique ID.
Name User assigned name. Can be modified anytime.
Comment User free text comment. Can be used for labels, reminders or any other purpose
Status
  • Normal
  • Creating
  • Deleting
  • Partial/Failed – At least one of the underlying RAID groups has failed, or the Pool metadata cannot be initialized at Start Of the Day.
Capacity Total available capacity for user data & system metadata.
Available Capacity Available (free) capacity to be used for User data. VPSA reserves 2% of the total Pool capacity for system metadata. If the VPSA needs more capacity for the metadata (very rare scenario), it will be consumed from the available capacity.
Metadata Capacity Metadata Capacity
Capacity State
  • Normal
  • Alert
  • Protected
  • Emergency

See Managing Pool Capacity Alerts for more details.

Mode
  • Simple – There are one or more concatenated RAID Groups.
  • Stripe – There are two or more striped RAID Groups.
  • Mixed – There are two or more concatenated and striped RAID Groups.
Type
  • Transactional Workloads
  • Repository Storage
  • Archival Storage
Stripe Size Applicable only for Pools of Striped mode (i.e. when data is striped between 2 or more RAID groups). The Stripe size is always 64KB.
Cached Yes/No – Indicates whether the Pool utilizes SSD for read/write caching
Cache COW Writes Yes/No – Indicates whether flash cache is used for internal snapshots Copy-On-Write Operations.Enabled by default. Disable only on rare cases where frequent snapshots cause extreme load of metadata operations. Consult Zadara support.
Raid Group(s) RAID Group name, or “Multiple (X)” where X denotes the number of RAID Groups in the Pool.
Created Date & time when the object was created.
Modified Date & time when the object was last modified.

imageAFA Each Pool of All Flash Array includes the following properties:

Property Description
  General
ID An internally assigned unique ID.
Name User assigned name. Can be modified anytime.
Comment User free text comment. Can be used for labels, reminders or any other purpose
Status
  • Normal
  • Creating
  • Deleting
  • Partial/Failed – At least one of the underlying RAID groups has failed, or the Pool metadata cannot be initialized at Start Of the Day.
Type
  • Transactional Workloads
  • Repository Storage
  • Archival Storage
Raid Group(s) RAID Group name, or “Multiple (X)” where X denotes the number of RAID Groups in the Pool.
Created Date & time when the object was created.
Modified Date & time when the object was last modified.
  Physical Capacity
Usable Capacity Total capacity of all RAID groups in the Pool
Used Capacity The total size of all data written in the Pool Used Capacity = Used by Volumes + Used by metadatra + Used by data copies
Used by Volumes Capacity used to store the Volumes data
Used by Data Copies Capacity used to store Snapshots and Clones
Used by Metadata Capacity used to store the Pool’s metadata
Free Capacity Available Capacity in the Pool that can be used for new Data and Metadata writes
Physical Capacity State
  • Normal
  • Alert
  • Protected
  • Emergency

See Managing Pool Capacity Alerts for more details.

  Virtual Capacity
Provisioned Capacity Sum of Pool’s Volumes and Clones capacities as seen by the hosts
Allocated Capacity Pool’s allocated address space of all Volumes, Snapshots and Clones
Effective Capacity Amount of data written in the pool by all volumes and can be accessed by hosts. Not including space taken by snapshots
Virtual Capacity State
  • Normal
  • Alert
  • Protected
  • Emergency

See Managing Pool Capacity Alerts for more details.

  Capacity Savings
Data Reduction Ratio Capacity savings by all data reduction techniques. Data Reduction Ratio = Effective Capacity / Used by Volumes
Deduplication Ratio Capacity savings by deduplication
Compression Ratio Capacity savings by compression
Thin Provision Ratio Capacity savings by thin provisioning technique. Thin Provision Ratio = Provisioned Capacity / Effective Capacity

RAID Groups

In the RAID Groups View This tab lists the RAID Groups allocated to the selected Pool. Each RAID Group includes the following information:

  • Name
  • Protection (RAID-1, RAID-5or RAID-6)
  • Status
  • Contributed Capacity

In the Segments View This tab shows the structure of pool made of concatinated or striped segments

image136


Volumes and Dest Volumes

These two tabs display the provisioned Volumes and the Provisioned Remote Mirroring Destination Volumes. Please note that the Dest Volumes are not displayed in the main Volumes page since most operations are not applicable to them. Displaying the list of the Dest Volumes in the Pools South Panel provides a complete picture of the Objects that consume capacity from the Pool. Each Volume includes the following information:

  • Name
  • Capacity (virtual, not provisioned)
  • Status
  • Data Type (Block or File-System)

Recycle Bin

By default when you delete a volume it moves to a Pool’s Recycle Bin for 7 days until it is permanently deleted. From the Recycle Bin an administrator can purge (permanently delete) or restore a volume.


Logs

Displays all event logs associated with this Pool.


Metering

The Metering Charts provide live metering of the IO workload associated with the selected Pool.

The charts display the metering data as it was captured in the past 20 “intervals”. An interval length can be set to one of the following: 1 Second, 10 seconds, 1 Minute, 10 Minutes, or 1 Hour. The Auto button lets you see continuously-updating live metering info (refreshed every 3 seconds).

Pool Metering includes the following charts:

Chart Description
IOPs The number of read and write SCSI commands issued to the Pool, per second.
Bandwidth (MB/s) Total throughput (in MB) of read and write SCSI commands issued to the Pool, per second.
IO Time (ms) Average response time of all read and write SCSI commands issued to the Pool, per selected interval .

Capacity Alerts

The Capacity Alerts tab lists the configurable attributes of the Pool Protection Mechanism. See Managing Pool Capacity Alerts for more details. You can modify the following attributes:

  • Physical Pool Alert Mode Threshold - “Alert me when it is estimated that the Pool will be at full physical capacity in X Minutes.”
    • Default Value: 360 minutes
  • Physical Pool Protection Mode Threshold - “Do not allow new Volumes, Shares, or Snapshots to be created when it is estimated that the Pool will be at full physical capacity in X Minutes.”
    • Default Value: 60 minutes
  • Physical Pool Calculation Window - “Calculate the estimated time until the Pool is full based on new capacity usage in the previous X minutes.”
    • Default Value: 60 minutes
  • Physical Pool Emergency Mode Threshold - “Delete snapshots, starting from the oldest, when there is less than the following physical capacity left in the Pool”
    • Default Value: 50 GB

imageAFA

  • Allocated Capacity Alert Mode Threshold - “Alert me when it is estimated that the Pool’s address space will be at full capacity in X Minutes.”
    • Default Value: 360 minutes
  • Allocated Capacity Protection Mode Threshold - “Do not allow new Volumes, Shares, or Snapshots to be created when it is estimated that the Pool’s address space will be at full capacity in X Minutes.”
    • Default Value: 60 minutes
  • Allocated Capacity Calculation Window - “Calculate the estimated time until the Pool’s address space is full based on new capacity usage in the previous X minutes.”
    • Default Value: 60 minutes
  • Allocated Capacity Emergency Mode Threshold - “Delete snapshots, starting from the oldest, when there is less than the following free address space left in the Pool”
    • Default Value: 5 GB

Performance Alerts

The Performance Alerts tab lists the Pool’s ability to send alerts when performance drops below expectations. See Managing Pool Performance Alerts for more details.


Managing Pool Capacity Alerts

The VPSA’s efficient and sophisticated storage provisioning infrastructure maximizes storage utilization, while providing key enterprise-grade data management functions. As a result, you can quite easily over-provision a Pool with Volumes, Snapshots and Clones, hence requiring a Pool Protection Mechanism to alert and protect when free Pool space is low.

The VPSA Pool Protection Mechanism is either time-based or capacity consumption based. The goal is to provide you sufficient time to fix the low free space situation by either deleting unused Volumes/Snapshots/Clones or by expanding the Pool’s available capacity (a very simple and quick process due to the elasticity of the VPSA and the Zadara Storage Cloud).

The VPSA measures the rate at which the Pool’s free space is consumed and calculates the estimated time left before running out of free space.

The following user-configurable parameters impact alerts and operations that are performed as part of the Pool Protection mechanism:

  • Physical Pool Capacity Alert Threshold – The estimated time (in minutes) before running out of free space or percentage used. When triggered an online support ticket is submitted and an email is sent to the VPSA user. When crossing this threshold the Free Capacity State changes to “Alert” and the available capacity will be shown in Yellow. A secondary “reminder” ticket and an email will be generated when only half of this threshold’s estimated time is left.

    • Default time: 600 minutes (10 hours)
    • Minimum: 1 minute (0 means disable this alert by time)

    or

    • Default Percentage: 90% full
    • Minimum: 1 % (0 means disable this alert by %)
  • Physical Pool Capacity Protection Threshold – The estimated time (in minutes) before running out of free space. When triggered the VPSA starts blocking the creation of new Volumes, Snapshots and Clones in that Pool. A support ticket and email are also generated. When crossing this threshold, the Free Capacity State changes to “Protect” and the available capacity will be shown in Red.

    • Default: 180 minutes (3 hour)
    • Minimum: 1 minute (0 means disable this alert by time)

    or

    • Default Percentage: 95% full
    • Minimum: 1 % (0 means disable this alert by %)
  • Physical Pool Capacity Emergency Threshold – When the Pool’s free capacity drops below this fixed threshold (in GB) or below the specified % threshold, the VPSA starts freeing Pool capacity by deleting older snapshots. The VPSA will delete one snapshot at a time, starting with the oldest snapshot, until it exceeds the Emergency threshold (i.e. when free capacity is greater than the threshold). A support ticket and email are also generated. When this threshold is crossed the Free Capacity State changes to “Emergency” and the available capacity will be shown in Red.

    • Default: 50 GB
    • Minimum: 1 GB

    or

    • Default Percentage: 99% full
    • Minimum: 1 % (0 means disable this alert by %)
  • Physical Pool Capacity Alert Interval - The size of the window (in minutes) that is used to calculate the rate at which free space is consumed. The smaller the window is the more this rate is impacted by intermediate changes in capacity allocations, which can result from changes in workload characteristics and/or the creation/deletion of new Snapshots and Clones.

    • Default: 60 minutes (1 hours)
    • Minimum: 1 minute

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imageAFA In addition to the physical capacity alerts, The All Flash VPSA provides alerts in case The Pool allocation (virtual address space) is near capacity.

Free Address Space = Allocation Limit – Allocated Capacity

The following user-configurable parameters impact alerts and operations that are performed as part of the Pool Protection mechanism:

  • Allocated Capacity Alert Threshold – The estimated time (in minutes) before running out of free address space. When triggered an online support ticket is submitted and an email is sent to the VPSA user. When crossing this threshold the Allocated Capacity Alert Mode changes to “Alert” and the available address sace will be shown in Yellow. A secondary “reminder” ticket and an email will be generated when only half of this threshold’s estimated time is left.
    • Default: 360 minutes (6 hours)
    • Minimum: 1 minute (0 means disable this alert)
  • Allocated Capacity Protection Threshold – The estimated time (in minutes) before running out of free address space. When triggered the VPSA starts blocking the creation of new Volumes, Snapshots and Clones in that Pool. A support ticket and email are also generated. When crossing this threshold, the Allocated Capacity Alert Mode changes to “Protect” and the available address space will be shown in Red.
    • Default: 60 minutes (1 hour)
    • Minimum: 1 minute (0 means disable this alert)
  • Allocated Capacity Alert Interval - The size of the window (in minutes) that is used to calculate the rate at which free address space is consumed. The smaller the window is the more this rate is impacted by intermediate changes in capacity allocations, which can result from changes in workload characteristics and/or the creation/deletion of new Snapshots and Clones.
    • Default: 60 minutes (1 hours)
    • Minimum: 1 minute
  • Allocated Capacity Emergency Threshold – When the Pool’s free address space drops below this fixed threshold (in GB), the VPSA starts freeing Pool capacity by deleting older snapshots. The VPSA will delete one snapshot at a time, starting with the oldest snapshot, until it exceeds the Emergency threshold (i.e. when free address space is greater than the threshold). A support ticket and email are also generated. When this threshold is crossed the Free Capacity State changes to “Emergency” and the available address space will be shown in Red.
    • Default: 5 GB
    • Minimum: 1 GB

Managing Pool Performance Alerts

A VPSA administrator has the option to set Pool Performance Alerts in addition to the default Pool Capacity Alerts. Performance Alerts are available for:

Read IOPS Limit – Creates an alert when the average read IOPS, during the past minute, for a Pool exceeds a user-specified threshold.

Read Throughput Limit - Creates an alert when, during the past minute, the average read MB/s for a Pool exceeds a user-specified threshold.

Read Latency Limit – Creates an alert when, during the past minute, the average read latency for a Pool exceeds a user-specified threshold.

Write IOPS Limit – Creates an alert when, during the past minute, the average write IOPS for a Pool exceeds a user-specified threshold.

Write Throughput Limit - Creates an alert when, during the past minute, the average write MB/s for a Pool exceeds a user-specified threshold.

Write Latency Limit – Creates an alert when, during the past minute, the average write latency for a Pool exceeds a user-specified threshold.