**** Work in Progress ****
The volumename.cfg file holds all the settings that tie all those LUNs together into a volume as we know it. It resides in the config folder of your metadata controller (/Library/Filesystems/Xsan/config/) and is definitely something you should back up!
Below is a .cfg file copied into the wiki, I will go through and explain what each line means and what role it plays.
Text in Red, I have added.
# ****************************************************************************
# A global section for defining file system-wide parameters.
# ****************************************************************************
FileLocksYes
GlobalSuperUserYes
QuotasYes
Enables quotas to be set and enforced.
WindowsSecurityYes
ForceStripeAlignmentYes
RAID arrays have a stripe size (block size x stripe breadth) where they give optimum performance, for example this cfg has a 2MB stripe size. The first 1MB of a LUN is used for the CV label, and without Force Stripe Alignment the first stripe written to the discs would be half way through a physical stripe. When set to 'YES' the first stripe would be written to the discs at the 2MB mark, aligning it with the physical stripe as to not half fill two stripes on the disk.
UnixIdFabricationOnWindowsYes
EnforceACLsYes
Enables ACLs to be set and enforced.
Debug0
AllocationStrategyRound
Sets storage pool allocation strategy between; Round, Balance & Fill.
The amount of blocks initially allocated when a file requests space, in this case 1MB (8 x 128k).
As the file grows, it is allocated space in chunks (of blocks), the size of which is outlined above (always rounded up to the nearest integer multiple of the InodeExpandMin).
1st Growth 40 (5MB)
2nd Growth 72 (9MB)
3rd Growth 104 (13MB)
Nth Growth 8+(Nx32)
The maximum number of blocks the inode can expand to before a new one is created. (This is will be rounded up to the nearest integer multiple of the InodeExpandMin)
BufferCacheSize32M
JournalSize16M
FsBlockSize128K
How large the blocks of data the file system writes, this is the smallest a file can be on the specific volume. All files are rounded up to integer multiples of this value.
InodeCacheSize8K
MaxConnections75
MaxLogSize10M
This sets how large a volumes cvlog file (located in - /Library/Filesystems/Xsan/data/volume/log/ ) can grow before a new file is started and a number suffixed to the now 'full' cvlog.
ThreadPoolSize128
UnixNobodyUidOnWindows-2
UnixNobodyGidOnWindows-2
# ****************************************************************************
# A disktype section for defining disk hardware parameters.
# ****************************************************************************
In my volume I have 6 LUNs as outlined below.
[DiskType metaType]
Sectors 976608427
SectorSize 512
[DiskType video1Type]
Sectors 5860595679
SectorSize 512
[DiskType video3Type]
Sectors 5860595679
SectorSize 512
[DiskType video5Type]
Sectors 5860595679
SectorSize 512
[DiskType video4Type]
Sectors 5860595679
SectorSize 512
[DiskType video2Type]
Sectors 5860595679
SectorSize 512
# ****************************************************************************
# A disk section for defining disks in the hardware configuration.
# ****************************************************************************
[Disk meta]
Status Up
Type metaType
[Disk video1]
Status Up
Type video1Type
[Disk video3]
Status Up
Type video3Type
[Disk video5]
Status Up
Type video5Type
[Disk video4]
Status Up
Type video4Type
[Disk video2]
Status Up
Type video2Type
# ****************************************************************************
# A stripe section for defining stripe groups.
# ****************************************************************************
[StripeGroup Meta]
Name of the stripe group.
Group is enabled. An example where you could need to play with this is where a storage pool linked to a affinity had died through the loss of a LUN and you wanted to try and recover data that was not spread across the failed LUN.
This stripe group / storage pool is exclusive to one task, in this case metadata so user data is not written to it.
This stripe group / storage pool has been set aside for Metadata & Journaling.
Fairly self explanatory.
Fairly self explanatory.
The strategy in which selects which LUN to write to next.
How many blocks are written to a LUN before moving onto the next.
LUN(s) added to the group / pool, in this case just the one.
[StripeGroup Video]
Status Up
Exclusive No
In the previous example this was set to 'Yes', as it was just for metadata. However this group / pool is for user data so therefore is not exclusive.
Metadata No
Journal No
Does not hold metadata or journaling, as we have a dedicated LUN for that.
Affinity Video
Read Enabled
Write Enabled
MultiPathMethod Rotate
StripeBreadth 16
Node video1 0
Node video3 1
Node video5 2
Node video4 3
Node video2 4
LUN(s) added to the group / pool, when the Multi Path Method is set to rotate, the filesystem will write to these LUNs in the order they are numbered (not the numbers in the cvlabel, rather the numbers added in the cfg after the LUN name). This config has been laid out to avoid hitting two controllers which are housed in the same chassis sequentially, as the cache coherence in an active-active failover performs best when time between the controllers being hit is evenly spaced.