[linux-lvm] (LONG) Delay when writing to LVM after boot
mcsontos at redhat.com
Fri Apr 19 11:48:14 UTC 2013
Likely a question for ext4 forum - I guess FS is reading and
caching additional metadata to find suitable block.
 explains the delay on first write
 explains no delay on subsequent writes
On 04/19/2013 03:16 AM, Ken Bass wrote:
> I have one LVG with one LV consisting of several physical drives, ranging
> from 500G to 3T, with a total size of 6.5T, formatted with ext4.
> After I boot the system, when anything writes a file to that LV, the write
> hangs for 1 minute or more, then continues at full speed with no errors.
> Some apps, though can't handle the delay, and report that the write fails.
> This does not occur with a small file ( < 50M or so ). But the first time a
> larger file is written, then the delay. And this delay occurs only one time.
> I have noticed something similar in the past with smaller LVs ( < 1T ), but
> the delay was insignificant then. But as I grew this LV, the delay
> I can run e2fsck on the LV, and even optimize directories (-D option), with
> no delay occurring.
> I have tried googling, but have not found any mention of something like
> this (maybe not using the right key words?). So, does this sound familiar
> to any LVM experts out there? Any suggestions?
> FWIW: I'm currently running Fedora 17 (64 bit), kernel
> 3.8.4-102.fc17.x86_64 (although I have seen this problem on 32 bit
> kernels/machines as well). I have 4 physical drives (500G, 1T, 1.5T, 3T),
> and non-raid configured.
> Some other info:
> [root at elmer ken]# lvmdiskscan
> /dev/vg_elmer/lv_swap [ 3.62 GiB]
> /dev/sda1 [ 500.00 MiB]
> /dev/vg_elmer/lv_root [ 23.81 GiB]
> /dev/sda2 [ 27.47 GiB] LVM physical volume
> /dev/VG_NAS/LV_NAS [ 5.46 TiB]
> /dev/sdb1 [ 2.73 TiB] LVM physical volume
> /dev/sdc1 [ 465.76 GiB] LVM physical volume
> /dev/sdd1 [ 931.51 GiB] LVM physical volume
> /dev/sde1 [ 1.36 TiB] LVM physical volume
> 3 disks
> 1 partition
> 0 LVM physical volume whole disks
> 5 LVM physical volumes
> [root at elmer ken]# lvdisplay
> --- Logical volume ---
> LV Path /dev/VG_NAS/LV_NAS
> LV Name LV_NAS
> VG Name VG_NAS
> LV UUID IO93PY-kFF2-19u7-33lX-m7Mg-8BZC-q12ttn
> LV Write Access read/write
> LV Creation host, time ,
> LV Status available
> # open 1
> LV Size 5.46 TiB
> Current LE 1430794
> Segments 5
> Allocation inherit
> Read ahead sectors auto
> - currently set to 256
> Block device 253:2
> [root at elmer ken]#
> (note: sda is separate physical drive with system/kernel only - vg_elmer-*)
> T IA
> linux-lvm mailing list
> linux-lvm at redhat.com
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
More information about the linux-lvm