Apple Xsan 2 (Third Edition) - Manual (Page 34)

Connect Devices to Specific Blades
If your Fibre Channel switch is based on a blade architecture, you might be able to
improve performance by:
Connecting pairs of devices that routinely exchange large volumes of data to the Â
same blade in the switch
Distributing loads across multiple blades instead of concentrating all of the load on
Â
one or two blades
Configuring RAID Systems
Follow these guidelines when you set up your RAID systems for use as Xsan LUNs.
Installing the Latest Firmware
To get the best performance and reliability from your RAID systems, install the latest
firmware.
Connecting RAID Systems to an Ethernet Network
For best performance, don’t connect RAID controller Ethernet management ports to
the SAN’s metadata network. Connect the ports to the separate Ethernet network that
you use for other types of network traffic, such as directory services, Internet access,
and remote Xsan management.
Choosing RAID Levels for LUNs
Use RAID 1 for metadata LUNs and RAID 5 for data LUNs.
Use RAID 1 for Metadata LUNs
RAID 1 (mirroring) can give slightly better performance than the default RAID 5
scheme for the small, two-drive metadata LUNs that Xsan uses to store volume
information. A single drive is almost always adequate for storing the primary volume
metadata. (10 GB of metadata space is enough for approximately 10 million files.)
The second, mirror drive protects you against metadata loss.
Use RAID 5 for Data LUNs
Most RAID systems are optimized for excellent performance and data redundancy
using a RAID 5 scheme. (RAID 5 stripes data across the available drives and also
distributes parity data across the drives.) Some RAID systems ship preconfigured
as RAID 5 LUNs. RAID 0 (striping with no parity) might give slightly better write
performance, but it provides no data recovery protection, so RAID 5 is always a better
choice for LUNs used to store user data.
34 Chapter 2 Planning a Storage Area Network