[mysql@mysqlu02?~]$?more?/etc/redhat-release?
Red?Hat?Enterprise?Linux?release?8.7?(Ootpa)
[mysql@mysqlu02?~]$?touch?test.txt
[mysql@mysqlu02?~]$?stat?test.txt
??File:?test.txt
??Size:?0???????????????Blocks:?0??????????IO?Block:?4096???regular?empty?file
Device:?fd05h/64773d????Inode:?144?????????Links:?1
Access:?(0644/-rw-r--r--)??Uid:?(??801/???mysql)???Gid:?(??800/???mysql)
Access:?2023-05-06?17:09:44.428050549?+0800
Modify:?2023-05-06?17:09:44.428050549?+0800
Change:?2023-05-06?17:09:44.428050549?+0800
?Birth:?2023-05-06?17:09:44.428050549?+0800

RHEL 7.9 XFS文件系統

[oracle@KerryDB?~]$?more?/etc/redhat-release?
Red?Hat?Enterprise?Linux?Server?release?7.9?(Maipo)
[oracle@KerryDB?~]$?touch?test.txt
[oracle@KerryDB?~]$?stat?test.txt
??File:?‘test.txt'
??Size:?0???????????????Blocks:?0??????????IO?Block:?4096???regular?empty?file
Device:?fd03h/64771d????Inode:?4238838?????Links:?1
Access:?(0644/-rw-r--r--)??Uid:?(??700/??oracle)???Gid:?(??600/oinstall)
Access:?2023-05-06?17:03:42.964517675?+0800
Modify:?2023-05-06?17:03:42.964517675?+0800
Change:?2023-05-06?17:03:42.964517675?+0800
?Birth:?-
[oracle@KerryDB?~]$

stat命令的Birth字段表示文件的創(chuàng)建時間，該屬性是ext4的新功能（當然也適用于xfs文件系統），也稱為crtime或btime，但是當前兩個測試環(huán)境的文件系統為xfs,之前也在xfs文件系統中測試過，發(fā)現xfs不支持creation time. 但是從xfs v5開始，xfs已經支持creation time，文檔[1]中已有闡述,如下所示：

/*?version?5?filesystem?(inode?version?3)?fields?start?here?*/
?????__le32????????????????????di_crc;
?????__be64????????????????????di_changecount;
?????__be64????????????????????di_lsn;
?????__be64????????????????????di_flags2;
?????__be32????????????????????di_cowextsize;
?????__u8??????????????????????di_pad2[12];
?????xfs_timestamp_t???????????di_crtime;
?????__be64????????????????????di_ino;
?????uuid_t????????????????????di_uuid;
};
*di_crtime*::
Specifies?the?time?when?this?inode?was?created.

但是上面這個差異現象，還是讓我有點好奇，因為兩個測試環(huán)境對應的xfs版本都是v5，如下所示。

KerryDB這臺機器的xfs版本信息：

Oracle用戶:

$?uname?-r
3.10.0-1160.80.1.el7.x86_64
$?dmesg?|?grep?-iE?'xfs.*\s+mounting'?|?head?-1
[????4.041026]?XFS?(dm-0):?Mounting?V5?Filesystem

root用戶:

#?xfs_db?-r?/dev/mapper/vg00-home
xfs_db>?version
versionnum?[0xb4b5+0x18a]?=?V5,NLINK,DIRV2,ATTR,ALIGN,LOGV2,EXTFLG,MOREBITS,ATTR2,LAZYSBCOUNT,PROJID32BIT,CRC,FTYPE
xfs_db>

mysqlu02這臺機器的xfs版本信息：

mysql用戶：

$?dmesg?|?grep?-iE?'xfs.*\s+mounting'?|?head?-1
[????7.654324]?XFS?(dm-0):?Mounting?V5?Filesystem

root用戶：

#?xfs_db?-r?/dev/mapper/vg00-home
xfs_db>?version
versionnum?[0xb4b5+0x18a]?=?V5,NLINK,DIRV2,ATTR,ALIGN,LOGV2,EXTFLG,MOREBITS,ATTR2,LAZYSBCOUNT,PROJID32BIT,CRC,FTYPE,FINOBT,SPARSE_INODES,REFLINK
xfs_db>

那么到底是什么原因導致。Google搜索了相關資料，原來，如果stat命令查看xfs文件系統的文件時，如果要Birth字段不顯示空置，必須滿足幾個條件，一個是xfs的版本為v5，另外，對操作系統內核版本也有要求（如下所示）