Hi!
I'd like to create a xfs-formatted filesystem in an lvm logical volume
that resides on a software raid5 device.
Searching the list archives, I've found that performance should be ok
using an internal log for kernel versions > 2.4.18. Additionally, I
found a recommendation to use log version 2.
However, when creating the filesystem, the kernel reports that the cache
buffer size is reduced to 512 bytes:
# mkfs.xfs -l version=2 /dev/vg_raid5/lv_images
raid5: switching cache buffer size, 1024 --> 512
Are there additional arguments needed for mkfs.xfs?
The first reduction of cache buffer size occurs when activating lvm:
LVM version 1.0.7(28/03/2003) module loaded
loop: loaded (max 8 devices)
raid5: switching cache buffer size, 4096 --> 1024
Does this mean a performance penalty? Is there a way to avoid these
switches?
Is it still recommended to use an external log? How should the log be
configured?
Thanks in advance,
--leo
P.S.: Additional info:
# cat /etc/fedora-release
Fedora Core release 1 (Yarrow)
# uname -r
2.4.22-1.2115.nptl_22.rhfc1.at
# rpm -q xfsprogs
xfsprogs-2.6.2-0_7.rhfc1.at
# cat /proc/mdstat
Personalities : [raid5]
read_ahead 1024 sectors
md0 : active raid5 hdg1[0] hdi1[1] hdk1[2] hdm1[3] hdo1[4]
976751616 blocks level 5, 32k chunk, algorithm 2 [5/5] [UUUUU]
# mkfs.xfs -l version=2 /dev/vg_raid5/lv_images
meta-data=/dev/vg_raid5/lv_images isize=256 agcount=16,
agsize=8192000 blks
= sectsz=512
data = bsize=4096 blocks=131072000, imaxpct=25
= sunit=0 swidth=0 blks, unwritten=1
naming =version 2 bsize=4096
log =internal log bsize=4096 blocks=32768, version=2
= sectsz=512 sunit=0 blks
realtime =none extsz=65536 blocks=0, rtextents=0
# pvdisplay /dev/md0
--- Physical volume ---
PV Name /dev/md0
VG Name vg_raid5
PV Size 931.50 GB [1953503232 secs] / NOT usable 64.19 MB
[LVM: 186 KB]
PV# 1
PV Status available
Allocatable yes
Cur LV 1
PE Size (KByte) 65536
Total PE 14903
Free PE 6903
Allocated PE 8000
PV UUID d63Tg4-A41Z-4JXb-FwuV-wIik-QuVh-k2XW7E
# vgdisplay /dev/vg_raid5
--- Volume group ---
VG Name vg_raid5
VG Access read/write
VG Status available/resizable
VG # 0
MAX LV 256
Cur LV 1
Open LV 0
MAX LV Size 2 TB
Max PV 256
Cur PV 1
Act PV 1
VG Size 931.44 GB
PE Size 64 MB
Total PE 14903
Alloc PE / Size 8000 / 500 GB
Free PE / Size 6903 / 431.44 GB
VG UUID 1f13FE-qPVM-1CSB-0gAu-Fe07-5TlS-ElliwA
--
-----------------------------------------------------------------------
Alexander (Leo) Bergolth leo@xxxxxxxxxxxxxxxxx
WU-Wien - Zentrum fuer Informatikdienste http://leo.wu-wien.ac.at
Computers are like air conditioners -
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