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 by Lenovo Storage V series),
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 Lenovo Storage V series.
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 Lenovo Storage V series 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.
Table 1 compares the
maximum
volume capacity for each extent size. The
maximum is different for
thin-provisioned volumes. Because the
Lenovo Storage V series 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
Lenovo Storage V series 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.