Partitioning and File System Considerations

Assuming that three volumes were created from the disk pool, and if multipath is enabled, you should see a total of 6 mapped devices, as in the following example:

rroot@stlrx300s7-102:~# ls -l /dev/mapper
total 0
lrwxrwxrwx 1 root root       7 May  5 15:20 360080e50003220a80000017353450e3f -> ../dm-0
lrwxrwxrwx 1 root root       7 May  5 15:20 360080e50003222300000019153450e18 -> ../dm-1
lrwxrwxrwx 1 root root       7 May  5 15:20 360080e50003222300000019053450e18 -> ../dm-2
crw------- 1 root root 10, 236 May  5 15:20 control
            

Now we use the parted command to partition the mapped devices:

root@stlrx300s7-102:/dev/mapper# luns=`ls|grep -v control`
root@stlrx300s7-102:/dev/mapper# for i in $luns
> do
> parted -a optimal -s --  /dev/mapper/$i mklabel gpt mkpart primary xfs 0% 100%
> done
root@stlrx300s7-102:/dev/mapper# ls -l /dev/dm-
dm-0  dm-1  dm-2  dm-3  dm-4  dm-5  dm-6  dm-7  dm-8
root@stlrx300s7-102:/dev/mapper# ls -l /dev/mapper
total 0
lrwxrwxrwx 1 root root       7 May  5 15:29 360080e50003220a80000017353450e3f -> ../dm-0
lrwxrwxrwx 1 root root       7 May  5 15:29 360080e50003220a80000017353450e3f1 -> ../dm-3
lrwxrwxrwx 1 root root       7 May  5 15:29 360080e50003220a80000017353450e3f-part1 -> ../dm-4
lrwxrwxrwx 1 root root       7 May  5 15:29 360080e50003222300000019053450e18 -> ../dm-2
lrwxrwxrwx 1 root root       7 May  5 15:29 360080e50003222300000019053450e18p1 -> ../dm-5
lrwxrwxrwx 1 root root       7 May  5 15:29 360080e50003222300000019053450e18-part1 -> ../dm-6
lrwxrwxrwx 1 root root       7 May  5 15:29 360080e50003222300000019153450e18 -> ../dm-1
lrwxrwxrwx 1 root root       7 May  5 15:29 360080e50003222300000019153450e18p1 -> ../dm-7
lrwxrwxrwx 1 root root       7 May  5 15:29 360080e50003222300000019153450e18-part1 -> ../dm-8
crw------- 1 root root 10, 236 May  5 15:20 control
            

Swift currently requires that the underlying filesystem have support for extended attributes of the file system. While this requirement may be removed in a future release of Swift, as of the Havana release the recommended filesystem type is XFS.

Internal volumes created in a DDP layout resemble a traditional RAID 6 volume with the following parameters:

These parameters can be leveraged to configure the file system for optimal performance with the LUN. When a file system is created on a logical volume device, mkfs.xfs automatically queries the logical volume to determine appropriate stripe unit and stripe width values, unless values are passed at the time of filesystem creation; for example:

# ls -l /dev/mapper/|grep part|awk '{print $9}'
360080e50003220a80000017353450e3f-part1
360080e50003222300000019053450e18-part1
360080e50003222300000019153450e18-part1
# parts=`ls -l /dev/mapper/|grep part|awk '{print $9}'`
# for i in $parts
> do
> mkfs.xfs -d su=131072,sw=8 -i size=1024 $i
> done
    

	Tip
	You can verify that the partition was successfully created and is properly aligned by using the parted command: # parted /dev/mapper/360a9800043346852563444717a513571 align-check optimal 1 1 aligned

You can verify that the underlying filesystem has the correct values for stripe unit and stripe width by using the xfs_info command:

mount -t xfs -o nobarrier,noatime,nodiratime,inode64 /dev/mapper/360080e50003220a80000017353450e3f-part1 /disk1
# xfs_info /disk1
meta-data=/dev/mapper/360080e50003220a80000017353450e3f-part1 isize=1024   agcount=4, agsize=83623808 blks
         =                       sectsz=512   attr=2
data     =                       bsize=4096   blocks=334495232, imaxpct=5
         =                       sunit=32     swidth=256 blks
naming   =version 2              bsize=4096   ascii-ci=0
log      =internal               bsize=4096   blocks=163328, version=2
         =                       sectsz=512   sunit=32 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
    

sunit and swidth are shown in bsize (block size) units in the xfs_info command output.

stripe unit= 32 sunits * 4096 bsize (block size)= 131072 bytes = 128K
stripe width= 256 blocks * 4096 bsize = 1M = 128K * 8 drives
    

The sysctl fs.xfs.rotorstep can be used to change how many files are put into an XFS allocation group. Increasing the default number from 1 to 255 reduces seeks to multiple allocation groups. NetApp has observed improved performance in some cases by increasing this number. You can put the following line in /etc/sysctl.conf to ensure this change is affected on each boot of the system:

fs.xfs.rotorstep = 255
    

When mounting the XFS filesystem that resides on the LUNs offered from the E-Series storage, be sure to use the following mount options:

mount –t xfs –o “nobarrier,noatime,nodiratime,inode64” \
/dev/mapper/nodeX /srv/node/sdb1
    

	Warning
	The mount points for the account, container, and object storage are not managed by Swift; therefore, you must use the standard Linux mechanisms (e.g. /etc/fstab) to ensure that the mount points exist and are mounted before Swift starts.