HP StorageWorks Scalable File Share - Manual (Page 100)

Creating and modifying file systems 5–16
File system name
The file system name must be a maximum length of 32 characters and must not contain spaces.
HP recommends that you use a shorter name (not more than 10 characters). This will simplify administration
and make the displays easier to view.
Mount point
The mount point defined for the file system is the mount point that clients will use when mounting the file
system. Each client node that mounts the file system must have a directory with the same name as the file
system mount point. This directory is used as the mount point.
All clients must use the same mount point for a file system. The HP SFS system does not support different
clients mounting the same file system on different mount points.
You can accept the suggested default (based on the file system name) or specify a different mount point.
Stripe size
The file system stripe size is the default size for files created in the file system. However, this can be changed
on a file-by-file basis. You can specify the stripe size in KB (kilobytes) or MB (megabytes).
The following rules apply to the stripe size on the file system:
• The lower limit of the default stripe size for a file system is 4MB; if you set a file system stripe size of
less than this, the stripe size will default to 4MB.
• Where the stripe size is larger than the minimum required value, it must be an exact multiple of the
largest page size on the client nodes that will be mounting the file system.
You can determine the page size on a client node in one of the following ways:
• By using the
syscall getpagesize()
function; this returns the value of the
PAGE_SIZE
attribute.
• By entering the command shown in the following example at the operating system prompt. This
example assumes that the
python
package is available on the system:
# python -c "import os; print os.sysconf(os.sysconf_names[’SC_PAGE_SIZE’])"
Page sizes are 4KB on 32–bit systems; on 64–bit systems, page sizes are 4KB, 8KB, or 16KB. You may have
a mixed environment where client nodes have different page sizes. For this reason, you should consider that
what is a permissible stripe size on one set of client nodes may not be a permissible stripe size on another
set of client nodes. As an example, if you have ia64 client nodes with a page size of 16KB and ia32e client
nodes with a page size of 4KB; to access files on both architectures, the minimum stripe size on the file
system must be a multiple of 16KB.
Note that the
create filesystem
command suggests a stripe size of 4MB, which is a multiple of the
typical page sizes possible. Note too that the HP SFS system does not enforce the stripe size guidelines,
because client systems are independent of each other; therefore it is possible to create a file that is not
accessible on another client system.
MDS LUNs
You will be asked to specify whether the MDS service is to be mirrored across two LUNs, and which LUNs
are to be used for the MDS service. HP recommends that the MDS service is mirrored. To support this, you
will need to use two MDS LUNs for the file system, with each of the LUNs on a different SFS20 array. The
HP SFS software then mirrors the MDS data across both LUNs—this means that if one of the SFS20 arrays
fails, the MDS service continues to operate normally.
Note that you also have the option to mirror OST services (this is explained later); if you decide to mirror
the MDS service, this does not mean that you must mirror the OST services.