iStor iS12U3, User Manual

Page: 73 / 98

SATA II RAID Subsystem
User Manual 73
HDD Read Ahead Cache:
This option allows the users to disable the cache of the HDDs on the RAID
subsystem. In some HDD models, disabling the cache in the HDD is necessary to
prove the RAID subsystem functions correctly.
Volume Data Read Ahead:
This option allows the users to set the Volume Data Read Ahead function. Options
are: Normal, Aggressive, Conservative, and Disabled.
HDD Queue Depth:
The queue depth is the number of I/O operations that can be run in parallel on a disk
drive. HDD Queue Depth options are 1, 2, 4, 8, 16, and 32.
Disk Write Cache Mode:
The RAID subsystem supports Disk Write Cache Mode options: Auto, Enabled, and Disabled.
If the RAID subsystem has BBM (battery backup module), selecting the Auto option will
automatically enable Disk Write Cache. On the other hand, if there is no BBM, the Auto
option will disable Disk Write Cache.
Disk Capacity Truncation Mode:
The RAID subsystem use drive truncation so that drives from different vendors are
more likely to be able to be used as spares for each other. Drive truncation slightly
decreases the usable capacity of a drive that is used in the subsystem. Options are:
Multiples Of 10G : If you have several 120GB drives from different vendors,
chances are that the capacity varies slightly. For example, one drive might be
121.1 GB, and the other 120.4 GB. This drive truncation mode makes the
121.1 GB and 120.4 GB drives same capacity as 120 GB so that one could
replace the other.
Multiples Of 1G: If you have 120 GB drives from different vendors, chances
are that the capacity varies slightly. For example, one drive might be 121.1
GB, and the other 121.4 GB. This drive truncation mode makes the 121.1 GB
and 121.4 GB drives same capacity 121 GB
so that one could replace the other.
No Truncation : The capacity of the disk drive is not truncated.
MAC over Two TB:
Use this option to enable volume size over 2TB in MAC machine