From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <51712EFE.2000300@redhat.com> Date: Fri, 19 Apr 2013 13:48:14 +0200 From: Marian Csontos MIME-Version: 1.0 References: In-Reply-To: Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] (LONG) Delay when writing to LVM after boot Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: LVM general discussion and development Likely a question for ext4 forum - I guess FS is reading[1] and caching[2] additional metadata to find suitable block. [1] explains the delay on first write [2] explains no delay on subsequent writes -- Marian 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 > increased. > > 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@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@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@elmer ken]# > > (note: sda is separate physical drive with system/kernel only - vg_elmer-*) > > T IA > > ken > > > > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://www.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ >