&KDSWHU/*'78VHUV0DQXDO
//
11RRWWHHVVRRQ
QWWKKH
H&&RRQQIILLJJXXUUDDWWLLRRQ
QRRII55$$,,'
'
DDQQG
G
$$UU
UUDD\\VV''UULLYYHHVV
(1) Use preferably Logical Drives of the type
disk to build an Array Drive.
Of course, RAID Array Drives can be configured with Logical Drives of the type
chain
, too, but
the aspects of security should be taken into consideration as well. For regular RAID Array
Drives, type
disk
Logical Drives are used.
(2) The Logical Drives of an Array Drive should have the same storage capacity.
In order not to waste valuable storage capacity, you should only use Logical Drives that
have the same storage capacity for an Array Drive.
(3) Use different SCSI channels when setting up Logical Drives for Array Drives.
Alternate between SCSI channels A and B (and C, D, and E if available) when setting up
SCSI devices for Logical Drives. This configuration method has a considerable impact on a
Array Drive's performance. Always keep in mind that the data is written in stripes to the
Logical Drives. If the next drive to be accessed is connected to a different SCSI channel, in-
dependent and overlapping accesses are possible.
(4) The Hot Fix drive provides the utmost security.
One of the reasons for which
R
AID Array Drives are used definitely lies with the
r
edundancy
they provide, that is, the data security you still have even in the event of a hard disk failure,
thus resting assured against loss of data and time. For the purpose of the following consid-
erations, we define the term
time without redundancy, TWR
. Set apart the time needed to
set up the Array Drive (state
build
), the time without redundancy should be kept as short as
possible. Let us assume that one of the hard disks of a RAID 5 Array Drive fails. The Array
Drive is without redundancy. TWR starts to run. Any superfluous prolongation of the TWR
(because you have to get a replacement hard disk, or because you did not realize the failure
immediately since you didn't hear the ICP Controller's alarm signal, or because nobody
checked the file server) increases the risk of data loss which will occur if a second hard disk
should fail. Therefore, new redundancy should be created as soon as possible and in an en-
tirely automated manner. Integrating a Hot Fix drive as an immediately available and auto-
replacing hard disk is the only way to keep the TWR as short as possible. Only a Hot Fix
drive can ensure optimal Array Drive security and constant data availability. Of course a Hot
Fix drive is not mandatory. If you control the Array Drive at regular intervals and immedi-
ately replace a defective hard disk (by shutting down the system or Hot Plug), you can do
without a Hot Fix drive.
(5) States of a RAIDYNE Array Drive
An Array Drive under the RAIDYNE operation system can assume seven different opera-
tional modes. An Array Drive is fully operational when in the
ready
state. All redundant in-
formation is present, that is, a hard disk can fail without impairing the functionality of the
Array Drive. This is the normal state of an Array Drive.
idle ready fail build rebuild expand error
Idle state.
This mode is characterized by the fact that the redundancy information of the
Array Drive has never been entirely created. An Array Drive assumes this state after its first
configuration and you exit GDTSETUP. If an error should occur while the array is in the
build
state, the array returns to the
idle
state (exception: if during the
build
state the dedicated
drive of RAID 4 fails, the state changes to
fail
).
Build state.
After the Array Drive has been configured for the first time, it changes from the
idle
to the
build
state as soon as you quit GDTSETUP. While the array is in the
build
state, re-
dundancy information is calculated and stored to the hard disks of the array.