Setting The Storage Array Cache Block Size - Dell PowerVault MD3000i Tuning Manual

Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices

4.6.3 Setting the Storage Array Cache Block Size

Configured through the CLI – This command is available at the storage array
level and effects all virtual disks and disk-groups.
Cache Block Size – Cache Block Size refers to the way cache memory is
segmented during allocation and affects all virtual disks in an array. On the
MD3000 and MD3000i, settings of 4KiB and 16KiB are available with 4KiB being
the default. A dramatic impact on performance can occur by choosing the
correct cache block size setting specific to the system's I/O profile. If the typical
I/O size is ≥16KiB, which is typical with sequential I/O, set the storage array
Cache Block Size to 16. For smaller (≤8KiB) I/O, especially in highly random or
transactional use cases, the default 4KiB setting is preferred. As this setting
affects all virtual disks on a storage array, changing it should be done with
attention to the I/O needs of the application.
Option
Drive Type
RAID Level
1
Segment Size
Write cache
with mirroring
Read-ahead
cache
Cache Block
1
Size
1
The MDSM CLI Guide and SMcli application may use the legacy terminology of KB to mean
10
Kilobytes, or 2
When formulating an SMcli command the KB postfix is however still required. IEEE 1541-2002
and IEC 60027-2 standards detail units of measurement prefixes for binary multiples.
December 2008 – Revision A01
Table 2: Storage Array Standard Configuration Specifications
MDSM GUI configuration templates
File System
Selectable
Selectable
128KiB
Fixed to on
On
Array Defaults to 4KiB
bytes. Throughout this whitepaper, the SI term kibibytes are used instead.
Database
Selectable
Selectable
128KiB
Fixed to on
Off
Multimedia
Selectable
Selectable
32KiB, 64KiB,
256KiB
128KiB, 256KiB,
Fixed to on
On
CLI Options
Selectable
0, 1/10, 5, 6
8KiB, 16KiB,
512KiB
On or Off
On or Off
4KiB, 16KiB
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