Databases Reference
In-Depth Information
Figure 5: Communication Structure using Ordinary Disks
•
D
c
:
Data size of control information
•
D
s
:
Data size of a target stream
•
N
d
:
The number of disks, excluding log disks
•
N
s
:
The number of stored streams
•
H:
Height of a Fat-btree stored into disks
•
T
rw
(D):
Time for read or write in a disk
•
T
cm
(D):
Time for communication between a host and a disk
The computing power also affects system performance, but it is negligible compared
with costs of disk access and network communication. Therefore, we ignore the
cost of computation in this estimation. We also assume that the structure of the
Fat-Btree is not changed by insert operations in this estimation, and that backup
disks can be decided uniquely.
3.2.1
The Cost of Operations in Ordinary Disks
Insert:
The followings are the main costs for an insert operation using ordinary
disks.
•
Cost of searching for the destination disk to insert the stream
-
Count of host-disk communications
(D
c
)
for traversing index: 2
H
