You can use the command-line interface (CLI) to create
a storage pool.
Attention: If you add an MDisk to a storage pool as an MDisk, any
data on the MDisk is lost. If you want to keep the data on an MDisk (for example, because you want
to import storage that was previously not managed bythe
system), you must create image mode volumes instead.
Assume that the system has been set up and that a back-end controller has been configured to
present new storage to the system.
If you are using a Lenovo Storage V series flash drive managed disk, ensure that you are familiar with the flash drive configuration rules.
If you intend to keep the volume allocation
within one storage system, ensure that all MDisks in the storage pool are presented by the same
storage system.
Ensure that all MDisks that are
allocated to a single storage pool are
of the same RAID type. If the storage pool has
more than one tier of storage, ensure that all MDisks in the same
tier are of the same RAID type. When using Easy Tier®,
all of the MDisks in a storage pool in
the same tier must be similar and have similar performance characteristics.
If you do not use Easy Tier®,
the storage pool must contain
only one tier of storage, and all of the MDisks in the storage pool must be similar and have
similar performance characteristics.
Consider the following factors as you decide how many
(storage pools) to
create:
- A volume can only be created using the storage from one storage
pool. Therefore, if you create small (storage pools), you might lose
the benefits that are provided by virtualization, namely more efficient management of free space and
a more evenly distributed workload for better performance.
- If any MDisk in an storage pool goes offline, all the
(volumes) in the storage pool go offline. Therefore you might
want to consider using different storage pools for different back-end controllers
or for different applications.
- If you anticipate regularly adding and removing back-end controllers or storage, this task is
made simpler by grouping all the MDisks that are presented by a back-end controller into one
storage pool.
- All the MDisks in a storage pool must have similar levels of performance or
reliability, or both. If a storage pool contains MDisks with different levels of
performance, the performance of the (volumes) in this group is limited by the
performance of the slowest MDisk. If a storage pool contains MDisks with
different levels of reliability, the reliability of the (volumes) in this group
is that of the least reliable MDisk in the group.
Note: When you create a pool with a new flash drive, the new flash drive is automatically formatted and set to a block size of 512 bytes.
Even with the best planning, circumstances can change and you must reconfigure your
(storage pools) after they have been created. The data migration facilities that
are provided by the system enable you to move data without disrupting I/O.
Choosing a storage pool extent size
Consider the following factors as you plan the extent size of each new
storage pool:
- You must specify the extent size when you create a new storage pool.
- You cannot change the extent size later; it must remain constant throughout the lifetime of the
storage pool.
- Storage pools can have different extent sizes; however, this places
restrictions on the use of data migration.
- The extent size affects the maximum size of a volume in the storage pool. A larger extent size
increases the total amount of storage that the system can manage, and a smaller extent size allows
more fine-grained control of storage allocation.
Maximum volume capacity by extent size compares the maximum
volume capacity for each extent size. The maximum is different for
thin-provisioned volumes. Because the
system
allocates a whole number of extents to each
volume that is created, using a
larger extent size might increase the amount of storage that is wasted at the end of each
volume. Larger extent sizes also reduces the ability of the
system to
distribute sequential I/O workloads across many MDisks and therefore can reduce the performance
benefits of virtualization.
Table 1. Maximum volume capacity by extent size| Extent size (MB) |
Maximum volume capacity in GB (not thin-provisioned volumes) |
Maximum volume capacity in GB (thin-provisioned volumes) |
|---|
| 16 |
2048 (2 TB) |
2000 |
| 32 |
4096 (4 TB) |
4000 |
| 64 |
8192 (8 TB) |
8000 |
| 128 |
16,384 (16 TB) |
16,000 |
| 256 |
32,768 (32 TB) |
32,000 |
| 512 |
65,536 (64 TB) |
65,000 |
| 1024 |
131,072 (128 TB) |
130,000 |
| 2048 |
262,144 (256 TB) |
260,000 |
| 4096 |
262,144 (256 TB) |
262,144 |
| 8192 |
262,144 (256 TB) |
262,144 |
Important: You can specify different extent
sizes for different storage pools;
however, you cannot migrate (volumes) between storage pools with different extent sizes.
If possible, create all your storage pools with
the same extent size.
Use the following steps to create a
storage pool:
Issue the mkmdiskgrp CLI command to
create a storage pool.This is an example of the CLI command you can issue to
create a storage pool:
mkmdiskgrp -name maindiskgroup -ext 32
-mdisk mdsk0:mdsk1:mdsk2:mdsk3
where maindiskgroup is
the name of the storage pool that
you want to create, 32 MB is the size of the extent
you want to use, and mdsk0, mdsk1, mdsk2, mdsk3 are
the names of the four MDisks that you want to add to the group.
You created and added MDisks to a storage
pool.
The following example provides a scenario where you want
to create a storage pool, but
you do not have any MDisks available to add to the group. You plan
to add the MDisks at a later time. You use the mkmdiskgrp CLI
command to create the storage poolbkpmdiskgroup and
later used the addmdisk CLI command to add mdsk4,
mdsk5, mdsk6, mdsk7 to the storage
pool.
- Issue mkmdiskgrp -name bkpmdiskgroup -ext 32
where
bkpmdiskgroup is the name of the storage pool that you want to
create and 32 MB is the size of the extent that you want to use.
- You find four MDisks that you want to add to the storage pool.
- Issue addmdisk -mdisk mdsk4:mdsk5:mdsk6:mdsk7 bkpdiskgroup
where
mdsk4, mdsk5, mdsk6, mdsk7 are the names of the MDisks that you want to add to
the storage pool and bkpdiskgroup is the name of the
storage pool for which you want to add MDisks.