F5 ARX-VE, Planning Manual

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Chapter 1
Site Planning
1 - 30
If the share’s server acknowledges a write, that acknowledgement must
amount to a guarantee that the data is written to disk. Use the following
steps to ensure that this guarantee extends from the NFS/CIFS mount point
all the way to the disk drive:
1. Configure the export/share for synchronous writes.
All CIFS shares support synchronous writes, as do most
implementations of NFS. For NFS servers that do not support
synchronous writes by default (such as many Linux
implementations), set the
sync option for the NFS export. To
improve volume performance, also set the no_wdelay option on the
export.
2. Mount the server’s file system for synchronous writes.
3. Configure the server’s hard drives for write-through (no
disk-caching).
Do not use any disk quotas on a metadata share, as they often report
incorrect information or do not conform to appropriate synchronous write
semantics.
NFS Metadata Shares Can Support Any Volume
An NFS metadata share can support any volume (NFS-only, CIFS-only, or
multi-protocol), whereas a CIFS metadata share can only support a volume
that also supports CIFS. This is because an NFS-only volume does not have
the CIFS credentials required to access a CIFS metadata-only share.
Avoid /vol/vol0 on NetApp
By default, a NetApp file server uses /vol/vol0 for its operating system,
making it a poor candidate for metadata storage. Typically, /vol/vol0 is
designed for very high reliability at the expense of fast access. Use a
NetApp volume that is configured for both reliability and speed.
Best Practices (Summary)
Choose a highly-available, synchronous file system that is dedicated
exclusively to metadata. The metadata share should be on a file system that
is not shared by any other device, should have multiple gigabytes of free
space, and should not be subjected to disk quotas. To increase the space, we
recommend configuring a discrete metadata-only share for each volume.
Choose a share with a balance of reliability and speed. If you use a NetApp
share, do not use /vol/vol0. An NFS metadata share supports all types of
managed volumes, whereas a CIFS metadata share is limited to volumes that
also support CIFS.
F5 Networks’ web-based application, Data Manager, can help you inventory
the shares/exports you plan to import and calculate the ARX metadata size
required. If you have access to Data Manager, you can use it to