Accusys ExaRAID GUI - Manual (Page 247)

Troubleshooting
6-4
7. Check I/O path connections
You have to make sure the bandwidth of I/O path can deliver the
performance you need. For example, if you install a quad-port 4Gbps
Fibre Channel HBA to a 4-lane PCIe 1.0 slot, your bandwidth will be limited
to 1GB/s bandwidth of the PCIe slot. You need also to check the data
rate of I/O paths is configured properly without degradation. For
example, your 4Gbps Fibre Channel channels are configured to run at
2Gbps rate, you need to check HBAs, switch, host interface ports, and
disk interface ports of the RAID system.
8. Check hard disk settings
Hard disks are the destination of all I/O and thus also important to
performance. For hard disks that have variable data rate (like 1.5 Gbps or
3 Gbps for SATA disks), please make sure the setting is correct by
checking the jumpers on the hard disk. You need also to make sure the
on-disk cache is turned on (see 2.8.1 Hard disks on page 2-57). Lastly, the
performance of hard disks varies from model to model, and even the
hard disk firmware revision could also cause differences, having the latest
revision helps you to get better performance.
9. Add memory at host computer or RAID controller
Adding more memory to your motherboard or RAID controller helps to
cache more data at memory to so as to reduce the number I/O access
to hard disks, especially helpful for data being accessed frequently.
Bigger memory also helps to avoid the performance glitch because more
data can be buffered for write commands or pre-fetched for read
commands, especially helpful for multiple video streams.
10. Check data layout on hard disks
A hard disk can deliver its best performance when servicing I/O access
on the inner tracks of disks, which provides data of lower block address
(LBA). As a result, to deliver high-throughput performance, place the
data in the beginning area of disk groups. To retain the performance of
data at the second half area of disk groups, you may use more hard disks
with striping.
11. Make the I/O workload distribute evenly
Check below to ensure the I/O workload are distributed evenly
• Data is transferred evenly through multiple host-interface
connections
• MPIO is enabled and dynamic load balancing is turned on
• I/O are processed evenly by the two controllers
• I/O are distributed evenly to multiple disk groups