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Chapter 3 Plan a SAN 51

Estimate metadata and journal data storage needs

To estimate the amount of space required for Xsan volume metadata, assume that 10

million les on a volume require approximately 10 GB of metadata on the volume’s

metadata storage pool.

The journal requires between 64 KB and 512 MB. Xsan congures a xed size when you

create a volume. Due to the small size, you can use a single RAID 1 LUN for the journal

storage pool. To maximize the performance benet of a separate journal storage pool,

dedicate entire physical disks to the RAID 1 LUN.

Choose an allocation strategy

If you choose a preset volume type when you set up a volume, Xsan Admin sets its

volume allocation strategy for you. Later, you can change the allocation strategy by

editing volume settings with Xsan Admin.

The allocation strategy you choose for a volume determines the order in which its

storage pools are lled with data. You can choose round robin, ll, or balance:

Â If you choose round robin, Xsan writes data to each storage pool in the volume in

turn. This is normally the best choice for performance.

Â If you choose ll, Xsan writes data to the rst storage pool in the volume until that

storage pool is full, and then moves to the next storage pool. This is a good choice

to keep a specic storage pool unused as long as possible.

Â If you choose balance, Xsan writes data to the storage pool that has the most free space.

Plan the Ethernet TCP/IP network

Ethernet connections are used in several ways in an Xsan SAN:

Xsan clients and metadata controllers use Ethernet to exchange volume metadata. Â

Xsan clients can use Ethernet for access to networks outside the SAN (campus or Â

corporate intranet or the Internet).

Xsan metadata controllers can use Ethernet connections for remote management. Â

RAID systems can use Ethernet connections for system management. Â

Fibre Channel switches can use Ethernet connections for switch management. Â

You have two options:

Use one Ethernet network for all trac. This is the less expensive option, but is also Â

less secure and might not provide the best performance.

Use two separate networks—one for metadata and another for all other IP trac. Â

This conguration is slightly more expensive (requiring two Ethernet adapters for

each computer and an additional switch) but oers greater security and better

performance because routine network trac doesn’t interfere with SAN volume

metadata trac.

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Apple Xsan Bedienungsanleitung Seite 51