LINUX-4 YOUR FILE SYSTEM (XFS)
XFS is a highly scalable,
high-performance file system which was originally designed at Silicon Graphics,
Inc. XFS is the default file system for Red Hat
Enterprise Linux 7
Main Features
XFS supports metadata journaling, which
facilitates quicker crash recovery. The XFS file system can also be
defragmented and enlarged while mounted and active. In addition, Red Hat
Enterprise Linux 7 supports backup and restore utilities specific to XFS.
- XFS is designed for large file systems and large file handling.
- XFS has on-line defragmentation tools
- XFS dramatically reduces start-up time by avoiding fsck delays.
- XFS has fast file system creation.
- XFS formatted disk capacity is greater than Ext3/4 even after removing the reserved blocks from the Ext3/4 file system
- ability to manage up to 500TB file systems with files up to 50TB in size,
- best performance for most workloads (especially with high speed storage and larger number of cores),
- less CPU intensive than most of the other file systems (better optimizations around lock contention, etc),
- the most robust at large scale (has been run at hundred plus TB sizes for many years),
- the most common file system in multiple key upstream communities: most common base for ceph, gluster and openstack more broadly,
- pioneered most of the techniques now in Ext4 for performance (like delayed allocation),
- no file system check at boot time,
- CRC checksum on all metadata blocks.
Other XFS Features
The XFS file system support:
Extended attributes (xattr)
This allows the system to associate several additional
name/value pairs per file. It is enabled by default.
Quota journaling
This avoids the need for lengthy quota consistency checks
after a crash.
Project/directory quotas
This allows quota restrictions over a directory tree.
Subsecond timestamps
This allows timestamps to go to the subsecond
Common Commands
for ext3/4 and XFS
|
Task
|
ext3/4
|
XFS
|
|
Create a file system
|
mkfs.ext4 or mkfs.ext3
|
mkfs.xfs
|
|
File system check
|
e2fsck
|
xfs_repair
|
|
Resizing a file system
|
resize2fs
|
xfs_growfs
|
|
Save an image of a file system
|
e2image
|
xfs_metadump and xfs_mdrestore
|
|
Label or tune a file system
|
tune2fs
|
xfs_admin
|
|
Backup a file system
|
dump and restore
|
xfsdump and xfsrestore
|
How to know that which FS
we are using,
[root@rhel7-server ~]# mount | grep
"^/dev"
/dev/sda5 on / type xfs (rw,relatime,seclabel,attr2,inode64,noquota)
/dev/sdb1 on /tdir1 type xfs (rw,relatime,seclabel,attr2,inode64,noquota)
/dev/sda3 on /home type xfs (rw,relatime,seclabel,attr2,inode64,noquota)
/dev/sda1 on /boot type xfs (rw,relatime,seclabel,attr2,inode64,noquota)
/dev/sdd1 on /tdir2 type xfs (rw,relatime,seclabel,attr2,inode64,noquota)
/dev/sde1 on /tdir3 type xfs (rw,relatime,seclabel,attr2,inode64,noquota)
[root@rhel7-server ~]# file -sL /dev/sda1
/dev/sda1: SGI XFS filesystem data (blksz 4096, inosz 256, v2 dirs)
[root@rhel7-server ~]# df -Th
Filesystem Type Size
Used Avail Use% Mounted on
/dev/sda5 xfs 15G
6.7G 8.0G 46% /
devtmpfs devtmpfs 488M
0 488M 0% /dev
tmpfs tmpfs 496M
80K 496M 1% /dev/shm
tmpfs tmpfs 496M
7.2M 489M 2% /run
tmpfs tmpfs 496M
0 496M 0% /sys/fs/cgroup
/dev/sdb1 xfs 1014M
33M 982M 4% /tdir1
/dev/sda3 xfs 1014M
33M 982M 4% /home
/dev/sda1 xfs 697M
123M 575M 18% /boot
/dev/sdd1 xfs 1014M
33M 982M 4% /tdir2
/dev/sde1 xfs 497M
26M 472M 6% /tdir3
[root@rhel7-server ~]# fsck -N /dev/sdd1
fsck from util-linux 2.23.2
[/sbin/fsck.xfs (1) -- /tdir2] fsck.xfs /dev/sdd1
[root@rhel7-server ~]# cat /etc/fstab
XFS INFO:
[root@rhel7-server ~]# xfs_info /dev/sde1
meta-data=/dev/sde1
isize=256 agcount=4,
agsize=32000 blks
= sectsz=512 attr=2, projid32bit=1
= crc=0
data = bsize=4096 blocks=128000, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=0
log =internal bsize=4096 blocks=853, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none
extsz=4096 blocks=0, rtextents=0
XFS CHECKING & REPAIRING:
[root@rhel7-server ~]# xfs_repair
Usage: xfs_repair [options] device
Options:
-f The device is a file
-L Force log zeroing. Do this as a last
resort.
-l logdev Specifies the device where the external log
resides.
-m maxmem Maximum amount of memory to be used in
megabytes.
-n No modify mode, just checks the
filesystem for damage.
-P Disables prefetching.
-r rtdev Specifies the device where the realtime
section resides.
-v Verbose output.
-c subopts Change filesystem parameters - use
xfs_admin.
-o subopts Override default behaviour, refer to man
page.
-t interval Reporting interval in seconds.
-d Repair dangerously.
-V Reports version and exits.
If only checking required then use “-n” flag
[root@rhel7-server ~]#
[root@rhel7-server ~]# xfs_repair /dev/sde1
xfs_repair: /dev/sde1 contains a mounted filesystem
xfs_repair: /dev/sde1 contains a mounted and writable filesystem
fatal error -- couldn't initialize XFS library
[root@rhel7-server ~]# umount /tdir3
[root@rhel7-server ~]#
[root@rhel7-server ~]# xfs_repair /dev/sde1
Phase 1 - find and verify superblock...
Phase 2 - using internal log
- zero log...
- scan filesystem
freespace and inode maps...
- found root inode
chunk
Phase 3 - for each AG...
- scan and clear agi
unlinked lists...
- process known inodes
and perform inode discovery...
- agno = 0
- agno = 1
- agno = 2
- agno = 3
- process newly
discovered inodes...
Phase 4 - check for duplicate blocks...
- setting up duplicate
extent list...
- check for inodes
claiming duplicate blocks...
- agno = 0
- agno = 1
- agno = 2
- agno = 3
Phase 5 - rebuild AG headers and trees...
- reset superblock...
Phase 6 - check inode connectivity...
- resetting contents of
realtime bitmap and summary inodes
- traversing filesystem
...
- traversal finished
...
- moving disconnected
inodes to lost+found ...
Phase 7 - verify and correct link counts...
done
[root@rhel7-server ~]#
SUSPEND XFS:
[root@rhel7-server /]# cd tdir2
[root@rhel7-server tdir2]# touch f1
[root@rhel7-server tdir2]# ls -l
total 0
-rw-r--r--. 1 root root 0 Nov 25 12:14 f1
[root@rhel7-server tdir2]# xfs_freeze -f /tdir2
[root@rhel7-server tdir2]# touch f2
It is in hung like situation…
Ctrl+c is also not working,
[root@rhel7-server ~]# ps -elf |grep -i touch
0 D root 7119
7035 0 80 0
- 26980 sb_sta 12:14 pts/2 00:00:00
touch f2
0 R root 7359
7133 0 80 0
- 28160 - 12:28 pts/1 00:00:00 grep --color=auto -i touch
[root@rhel7-server ~]#
From another terminal…
[root@rhel7-server ~]# xfs_freeze -u /tdir2
And bingo…
[root@rhel7-server tdir2]# ls -l
total 0
-rw-r--r--. 1 root root 0 Nov 25 12:14 f1
-rw-r--r--. 1 root root 0 Nov 25 12:29 f2
TO BE CONTINUED…………………………………………….
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