Dell PowerVault MD3000i - Manual (Page 13)

Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices
December 2008 – Revision A01 Page 13
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.
Table 2: Storage Array Standard Configuration Specifications
MDSM GUI configuration templates
Option
File System Database Multimedia
CLI Options
Drive Type Selectable Selectable Selectable Selectable
RAID Level Selectable Selectable Selectable 0, 1/10, 5, 6
Segment Size 1 128KiB 128KiB 256KiB
8KiB, 16KiB,
32KiB, 64KiB,
128KiB, 256KiB,
512KiB
Write cache
with mirroring
Fixed to on Fixed to on Fixed to on On or Off
Read-ahead
cache
On Off On On or Off
Cache Block
Size
1
Array Defaults to 4KiB 4KiB, 16KiB
1 The MDSM CLI Guide and SMcli application may use the legacy terminology of KB to mean
Kilobytes, or 2 10 bytes. Throughout this whitepaper, the SI term kibibytes are used instead.
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.