HP StorageWorks Scalable File Share - Manual (Page 90)

Creating and modifying file systems 5–6
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 file system stripe size:
• 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. The HP SFS software then mirrors the MDS data across
both LUNs—this means that if one of the MDS LUNs fails, the MDS service continues to operate normally.
The two MDS LUNs must be on the same EVA4000 array but each must be in a different disk group.
Number of OST services
The maximum number of OST services that the file system can have is determined by the number of available
OST LUNs.
LUN numbers and preferred servers
You will be asked to specify a LUN number and preferred server for each OST service. The list of available
OST LUNs will be displayed, as shown in the following example:
.
.
.
Here are the available LUNs which you can assign to OSTs:
LUN Array Controller Role Size (GB) Visible to Preferred
--- ----- ---------- ---- --------- ---------- ---------
8 2 A ost 290 south[3-4] -
9 2 B ost 290 south[3-4] -
10 3 A ost 290 south[3-4] -
11 3 B ost 290 south[3-4] -
13 4 A ost 290 south[5-6] -