QLogic 10000 Series Optimizing MS Exchange - Manual (Page 3)

SN0430948-00 Rev.B 11/13 3
Optimizing MS Exchange with the
QLogic 10000 Series Adapter
White Paper
Hard drives can be combined into RAID sets to increase the IOPS potential,
as shown in Figure 3. RAID sets also increase the presented capacity,
which allows for larger databases.
The Influence of RAID
In addition to greater IOPS potential and capacity, RAID sets offer various
degrees of high availability. A database will continue to be available even
after a physical drive failure. The cost of RAID is a specific IOPS penalty
that occurs during the write cycles that accounts for the redundancy
provided. Table 2 shows the write penalty for common RAID types.
The formulas used to calculate the potential IOPS of a solution using RAID
are as follows:
Raw IOPS = disk speed IOPS × disk quantity
Functional IOPS=(raw IOPS × write% / RAID penalty) + (raw IOPS × read%)
Note: Only write operations incur a penalty for RAID.
Specific Example from an IOPS Perspective
A storage solution is designed for 5,000 users who send and receive
100 messages a day (5,000 users × .120 = 600 IOPS). QLogic highly
recommends adding an additional 20 percent margin for unexpected
spikes in activity. This calculation produces an IOPS target workload
of 720.
This example uses RAID 5 to guard against disk failure, which incurs a
write penalty of 4. Deploying multiple database copies produces a read/
write ratio of 3:2 or 60 percent writes and 40 percent reads, as shown in
Table 3.
Note that the quantity of disks required to support this workload increases
substantially for slower disks. This increase is contrary to the thinking
of using slower-but-larger disks to meet capacity requirements. Larger
capacity serial advanced technology attachment (SATA) hard drives
offer an appealing price per gigabyte (GB), but do not have strong IOPS
capability. Higher-performing hard disks such as modern serial attached
SCSI (SAS) drives are more expensive per GB, but can better withstand the
rigors of the IOPS workload of Exchange.
FABRICCACHE OFFLOADS IOPS OVERHEAD
QLogic’s patent-pending FabricCache technology is an innovative
approach to releasing Microsoft Exchange Server from its heavy IOPS
burden. The QLogic 10000 Series Adapter resides within the mailbox
server and transparently caches the flow of information to and from the
Exchange database. Transparency means no special configuration or
tuning of Exchange Server is required. The flash-based cache captures the
most frequently used Exchange information and presents it at speeds often
five times faster than a regular call to storage, as shown in Figure 4. With
the IOPS load under control, storage designers now have greater flexibility
in the speed, size, and cost of their drive configuration.
Figure 3. Combining Drives Improves Aggregate Throughput
RAID Type Structure
Concatenated
Capacity 1
Write IOPS
Penalty
RAID 1
Equal number of data
disks and mirrored disks
(N × C) / 2 2
RAID 10
Equal number of striped
data disks and mirrored
disks
N / 2 2
RAID 5
Two or more data disks;
one striped disk for parity
N × C – (C × 1) 4
RAID 6
Two or more data disks;
two striped disks for
parity
N × C – (C × 2) 6
1
N = quantity of disks; C = capacity of each disk.
Table 2. Write Penalty for Common RAID Types
Disk
Speed
(RPM)
IOPS
per
Disk
Quantity
of Disks
Needed
Raw
IOPS
Write
IOPS
with
RAID 5
Penalty 1
Read
IOPS 2
Solution
IOPS
7.2k 85 16 1360 204 544 748
10k 125 11 1375 206 550 756
15k 175 8 1400 210 560 770
1
Raw IOPS × .6 / 4
2
Raw IOPS × .4
Table 3. IOPS Example