mkfs.xfs其中有以下两个选项：
-b block_size_options
This option specifies the fundamental block size of the filesystem. The valid
block_size_options are: log=value or size=value and only one can be supplied. The block
size is specified either as a base two logarithm value with log=, or in bytes with size=.
The default value is 4096 bytes (4 KiB), the minimum is 512, and the maximum is 65536 (64
KiB). Although mkfs.xfs will accept any of these values and create a valid filesystem, XFS
on Linux can only mount filesystems with pagesize or smaller blocks.
-s sector_size
This option specifies the fundamental sector size of the filesystem. The sector_size is
specified either as a value in bytes with size=value or as a base two logarithm value with
log=value. The default sector_size is 512 bytes. The minimum value for sector size is 512;
the maximum is 32768 (32 KiB). The sector_size must be a power of 2 size and cannot be made
larger than the filesystem block size.
嗯，这个描述是不是多余的。唯一暗示扇区可能是块内部使用的东西的是“sector_size 必须是 2 的幂大小，并且不能大于文件系统块大小”。也许这里的扇区是指底层块设备的扇区大小？默认值 512 字节表明了这一点。
显然，这只是猜测。我想知道在 XFS 的上下文中，块和扇区之间的区别是什么，以及它们如何影响文件系统性能。
答案1
扇区大小指底层块设备的扇区大小。它是磁盘的分配单元。这是磁盘的“硬件”属性。您可以使用以下命令查看它：
lsblk -o NAME,PHY-SEC,LOG-SEC,MAJ:MIN,SIZE,RO,TYPE,MOUNTPOINTS,VENDOR,MODEL,SERIAL
mkfs.xfs 的默认扇区大小是设备公布的扇区大小。如果 LOG-SEC 为 512，PHY-SEC 为 4096，则应使用 4096。如有疑问，请使用 PHY-SEC 以提高性能。
请注意，文件系统无法从扇区大小为 512 的块设备复制到物理扇区大小为 4096（或 8192）的块设备。您可以复制文件，但不能将其作为 PV 添加到 LVM VG 并用于pvmove移动数据。
块大小是文件系统的分配单位，又称簇大小。它是文件系统可以为文件或元数据分配的最小量。
这块大小需要更大，并且 a 应该是 2 的幂扇区大小。如果您打算只将文件系统用于大文件，则应增加块大小，否则保留默认值。
如果您使用 RAID 阵列或任何块设备抽象，则应遵循制造商文档以获得最佳性能。
出于性能原因，对齐分区也很重要。大多数现代 Linux 工具都会创建与 1MB 对齐的分区，这在大多数情况下都很好。
如果您不知道该怎么做，请保留默认设置。它们适用于正常用例。如果您想提高性能，请避免使用磁盘存储，使用基于 RAM 的存储，使用 zram（基于压缩 RAM 的交换），使用 SSD。
扇区大小由文件系统，并且手册页已过时。这是我的测试：
[mvutcovi@laptop-rh ~]$ truncate --size=1G xfs-test.img
[mvutcovi@laptop-rh ~]$ ls -lh xfs-test.img
-rw-r--r--. 1 mvutcovi mvutcovi 1.0G Jun 10 10:12 xfs-test.img
[mvutcovi@laptop-rh ~]$
[mvutcovi@laptop-rh ~]$ sudo losetup --sector-size=4096 --find --show xfs-test.img
/dev/loop0
[mvutcovi@laptop-rh ~]$ lsblk -o NAME,PHY-SEC,LOG-SEC,MAJ:MIN,SIZE,RO,TYPE,MOUNTPOINTS,VENDOR,MODEL,SERIAL /dev/loop0
NAME PHY-SEC LOG-SEC MAJ:MIN SIZE RO TYPE MOUNTPOINTS VENDOR MODEL SERIAL
loop0 4096 4096 7:0 1G 0 loop
[mvutcovi@laptop-rh ~]$
[mvutcovi@laptop-rh ~]$ sudo mkfs.xfs /dev/loop0
meta-data=/dev/loop0 isize=512 agcount=4, agsize=65536 blks
= sectsz=4096 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=1 bigtime=1 inobtcount=1 nrext64=0
data = bsize=4096 blocks=262144, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=4096 sunit=1 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
Discarding blocks...Done.
[mvutcovi@laptop-rh ~]$
[mvutcovi@laptop-rh ~]$ sudo wipefs -a /dev/loop0
/dev/loop0: 4 bytes were erased at offset 0x00000000 (xfs): 58 46 53 42
[mvutcovi@laptop-rh ~]$ sudo mkfs.xfs -s size=4096 /dev/loop0
meta-data=/dev/loop0 isize=512 agcount=4, agsize=65536 blks
= sectsz=4096 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=1 bigtime=1 inobtcount=1 nrext64=0
data = bsize=4096 blocks=262144, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=4096 sunit=1 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
Discarding blocks...Done.
[mvutcovi@laptop-rh ~]$
[mvutcovi@laptop-rh ~]$ sudo wipefs -a /dev/loop0
/dev/loop0: 4 bytes were erased at offset 0x00000000 (xfs): 58 46 53 42
[mvutcovi@laptop-rh ~]$ sudo mkfs.xfs -s size=512 /dev/loop0
illegal sector size 512; hw sector is 4096
Usage: mkfs.xfs
/* blocksize */ [-b size=num]
/* config file */ [-c options=xxx]
/* metadata */ [-m crc=0|1,finobt=0|1,uuid=xxx,rmapbt=0|1,reflink=0|1,
inobtcount=0|1,bigtime=0|1]
/* data subvol */ [-d agcount=n,agsize=n,file,name=xxx,size=num,
(sunit=value,swidth=value|su=num,sw=num|noalign),
sectsize=num
/* force overwrite */ [-f]
/* inode size */ [-i perblock=n|size=num,maxpct=n,attr=0|1|2,
projid32bit=0|1,sparse=0|1,nrext64=0|1]
/* no discard */ [-K]
/* log subvol */ [-l agnum=n,internal,size=num,logdev=xxx,version=n
sunit=value|su=num,sectsize=num,lazy-count=0|1]
/* label */ [-L label (maximum 12 characters)]
/* naming */ [-n size=num,version=2|ci,ftype=0|1]
/* no-op info only */ [-N]
/* prototype file */ [-p fname]
/* quiet */ [-q]
/* realtime subvol */ [-r extsize=num,size=num,rtdev=xxx]
/* sectorsize */ [-s size=num]
/* version */ [-V]
devicename
<devicename> is required unless -d name=xxx is given.
<num> is xxx (bytes), xxxs (sectors), xxxb (fs blocks), xxxk (xxx KiB),
xxxm (xxx MiB), xxxg (xxx GiB), xxxt (xxx TiB) or xxxp (xxx PiB).
<value> is xxx (512 byte blocks).
[mvutcovi@laptop-rh ~]$
[mvutcovi@laptop-rh ~]$ sudo wipefs -a /dev/loop0
[mvutcovi@laptop-rh ~]$ sudo losetup --detach /dev/loop0
[mvutcovi@laptop-rh ~]$ sudo losetup --sector-size=512 --find --show xfs-test.img
/dev/loop0
[mvutcovi@laptop-rh ~]$ sudo mkfs.xfs /dev/loop0
meta-data=/dev/loop0 isize=512 agcount=4, agsize=65536 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=1 bigtime=1 inobtcount=1 nrext64=0
data = bsize=4096 blocks=262144, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
Discarding blocks...Done.
[mvutcovi@laptop-rh ~]$
[mvutcovi@laptop-rh ~]$ sudo wipefs -a /dev/loop0
/dev/loop0: 4 bytes were erased at offset 0x00000000 (xfs): 58 46 53 42
[mvutcovi@laptop-rh ~]$ sudo mkfs.xfs -s size=4096 /dev/loop0
meta-data=/dev/loop0 isize=512 agcount=4, agsize=65536 blks
= sectsz=4096 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=0
= reflink=1 bigtime=1 inobtcount=1 nrext64=0
data = bsize=4096 blocks=262144, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=4096 sunit=1 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
Discarding blocks...Done.
[mvutcovi@laptop-rh ~]$
以下是其代码部分：
/* set configured sector sizes in preparation for checks */
if (!cli->sectorsize) {
/*
* Unless specified manually on the command line use the
* advertised sector size of the device. We use the physical
* sector size unless the requested block size is smaller
* than that, then we can use logical, but warn about the
* inefficiency.
*
* Set the topology sectors if they were not probed to the
* minimum supported sector size.
*/
if (!ft->lsectorsize)
ft->lsectorsize = dft->sectorsize;
答案2
简短的回答是块大小是最小分配大小，而扇区大小是底层物理设备扇区大小。然而，如此简洁的答案无法传达块和扇区大小之间的真正区别。
要理解的关键点是扇区大小是个原子写入大小底层物理设备的大小——换句话说，预计彻底成功或失败， 和不中间结果（即：部分写入）。这个概念对于 XFS 日志保护措施极其重要：错误配置扇区大小意味着冒险进入危险境地。
块大小是一个更“普通”的单位：它描述了文件数据的最小文件系统分配。在具有 4k 块大小的文件系统上，写入单个字节的数据（即：）echo -n 0 > /root/test.file将产生具有 4K 真实大小的文件：
[root@localhost ~]# echo -n 0 > test.file
[root@localhost ~]# stat test.file
File: test.file
Size: 1 Blocks: 8 IO Block: 4096 regular file
Device: fd00h/64768d Inode: 100664426 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Context: unconfined_u:object_r:admin_home_t:s0
Access: 2023-06-10 17:47:50.973092242 +0200
Modify: 2023-06-10 17:47:50.974092238 +0200
Change: 2023-06-10 17:47:50.974092238 +0200
Birth: 2023-06-10 17:47:50.973092242 +0200
[root@localhost ~]# du -hs test.file
4.0K test.file
边注：从中可以看出stat，Linux 内部以 512B 大小的“逻辑扇区”为单位计算大小（在上面的例子中，8x 512B“linux”块 = 1x 4K XFS 块）。
简短的总结是，虽然块大小“仅仅”是一个优化参数，扇区大小应该是正确的（因此可以自动检测）——或者崩溃/断电时文件系统可能损坏。