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Re: [linux-lvm] LVM incredible slow with Kernel 2.6.11



On Fri, Jun 30, 2006 at 09:32:13AM +0200, Cristian Livadaru wrote:
> On Thu, Jun 29, 2006 at 06:15:23PM +0200, Dieter St?ken wrote:
> > Cristian Livadaru wrote:
> > > me again ... isn't there anybody that could give ANY hint on what's
> > > wrong?
> > > 
> > > I did some test with dd and the result is terrible!
> > > 
> > > LVM
> > > explendidos:/shared# dd if=/dev/zero of=test1.dd bs=64 count=1000
> > > 1000+0 records in
> > > 1000+0 records out
> > > 64000 bytes transferred in 20.019969 seconds (3197 bytes/sec)
> > 
> > seems the data gets written synchronously without any buffering.
> > Thus each write is delayed until the data is really written to
> > disk. For a 5400 RPM disk you get 90 transactions per seconds.
> > This gives about 10 seconds for 1000 chunks. "bs=64" means
> > 64 bytes! so each sector will be written multiple times.
> > So may be the system even reads in each sector again each time
> > before writing it, thus it takes two turns which gives 20 seconds.
> > 
> > Unfortunately I can't tell why this happens :-(
> > 
> > May be "direct IO" takes place (like for oflags=direct),
> 
> where could I check this? 
> 
> > or this is some configuration option of LVM, i don't know about.
> > Try using "hdparm" to see, if DMA etc. is enabled. Have a look
> 
> no matter how it's set, the result is always the same.
> I could'nt find any usefull information in any logfiles, I enabled LVM
> verbose mode and debug output but still nothing was found.
> 
> > into /var/log/messages or use "dmesg" for nay hardware problems.
> > I recently discovered the "blockdev" command. Do you use any special
> I have read in some posts on the mailinglist about blockdev but not
> quite sure on how I could use it to solve my problem.
> 
> > ext3 feature? You may try "tune2fs -o journal_data_writeback".
> > If you don't have relevant data on the LV, you may try to write
> > to the LV device directly. Is it slow for read, too? try "hdparm -t"
> 
> hdparm -t /dev/share/sharevg
> 
> /dev/share/sharevg:
>  Timing buffered disk reads:  146 MB in  3.01 seconds =  48.50 MB/sec
>  HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate
>  ioctl for device
> 
> I tried tune2fs but it didn't get any better.
> I also dont understand why with kernel 2.4 I get about 5mb/s instead of
> the 350kb/s 
> not that 5mb would be great but still, much better then 350kb/s
> 
> Maybee I should mention that this is some "want-to-be" raid controler
> that was on the mainboard.
> 
> 0000:00:0e.0 RAID bus controller: Triones Technologies, Inc. HPT374 (rev
> 07)
> 
 
very strange, I just created a lvm on to other disks the size of this
lvm is only 1gb and I did the dd test in there and it was way better.

here the config of my slow LVM, 2x 300GB 

cat /etc/lvm/backup/share
# Generated by LVM2: Fri Jun  9 18:26:30 2006

contents = "Text Format Volume Group"
version = 1

description = "Created *after* executing '/sbin/vgcfgbackup'"

creation_host = "esplendidos"   # Linux esplendidos 2.4.27-2-386 #1 Thu
Jan 20 10:55:08 JST 2005 i686
creation_time = 1149877590      # Fri Jun  9 18:26:30 2006

share {
        id = "6szXKe-QPvJ-t14I-kF13-0JSc-bevq-dv4KBL"
        seqno = 2
        status = ["RESIZEABLE", "READ", "WRITE"]
        extent_size = 8192              # 4 Megabytes
        max_lv = 0
        max_pv = 0

        physical_volumes {

                pv0 {
                        id = "g3jfAR-Z2Ka-SCgr-08QB-8WBn-5g4h-jXLrn1"
                        device = "/dev/hde1"    # Hint only

                        status = ["ALLOCATABLE"]
                        pe_start = 384
                        pe_count = 71541        # 279.457 Gigabytes
                }

                pv1 {
                        id = "kYQB4j-fYV9-3NUa-g0Sg-H4Bk-Kx5F-wRO9G1"
                        device = "/dev/hdg1"    # Hint only

                        status = ["ALLOCATABLE"]
                        pe_start = 384
                        pe_count = 71541        # 279.457 Gigabytes
                }
        }

        logical_volumes {

                sharevg {
                        id = "KdvcJ9-ZLMP-AJYA-soGK-qHfy-UtrX-PpV9Kv"
                        status = ["READ", "WRITE", "VISIBLE"]
                        segment_count = 2

                        segment1 {
                                start_extent = 0
                                extent_count = 71541    # 279.457
Gigabytes

                                type = "striped"
                                stripe_count = 1        # linear

                                stripes = [
                                        "pv0", 0
                                ]
                        }
                        segment2 {
                                start_extent = 71541
                                extent_count = 71541    # 279.457
Gigabytes

                                type = "striped"
                                stripe_count = 1        # linear

                                stripes = [
                                        "pv1", 0
                                ]
                        }
                }
        }
}


and here the config of the new lvm on the other disks:


cat /etc/lvm/backup/vhostvg
# Generated by LVM2: Fri Jun 30 11:15:54 2006

contents = "Text Format Volume Group"
version = 1

description = "Created *after* executing 'lvcreate -L200M -nvm02swaplv
vhostvg'"

creation_host = "esplendidos"   # Linux esplendidos 2.6.11.12-xen0 #3
Thu Jun 29 15:47:52 CEST 2006 i686
creation_time = 1151658954      # Fri Jun 30 11:15:54 2006

vhostvg {
        id = "bZljKZ-0k6u-kuo5-4tGM-MxF2-oft4-R2R9mf"
        seqno = 5
        status = ["RESIZEABLE", "READ", "WRITE"]
        extent_size = 8192              # 4 Megabytes
        max_lv = 0
        max_pv = 0

        physical_volumes {

                pv0 {
                        id = "6POjat-zX5c-q7g5-KeRm-2ZmG-CAv4-odYFrt"
                        device = "/dev/hdi1"    # Hint only

                        status = ["ALLOCATABLE"]
                        pe_start = 384
                        pe_count = 29311        # 114.496 Gigabytes
                }

                pv1 {
                        id = "VaOcDQ-wyN5-5ahB-UF3y-zcTw-7e1U-PnJUnJ"
                        device = "/dev/hdk1"    # Hint only

                        status = ["ALLOCATABLE"]
                        pe_start = 384
                        pe_count = 29311        # 114.496 Gigabytes
                }
        }

        logical_volumes {

                vm01lv {
                        id = "nfdL2Z-NzUL-K9Ci-EF4L-izCq-qbnl-ZI6foI"
                        status = ["READ", "WRITE", "VISIBLE"]
                        segment_count = 1

                        segment1 {
                                start_extent = 0
                                extent_count = 256      # 1024 Megabytes

                                type = "striped"
                                stripe_count = 1        # linear

                                stripes = [
                                        "pv0", 0
                                ]
                        }
                }

                vm01swaplv {
                        id = "byPo9V-48mm-lfts-HZ4a-D21I-Y7Qt-573te9"
                        status = ["READ", "WRITE", "VISIBLE"]
                        segment_count = 1

                        segment1 {
                                start_extent = 0
                                extent_count = 125      # 500 Megabytes

                                type = "striped"
                                stripe_count = 1        # linear

                                stripes = [
                                        "pv0", 256
                                ]
                        }
                }

                vm02lv {
                        id = "up70a7-RETo-RvPI-liCc-ptdc-1qjA-MXrnsG"
                        status = ["READ", "WRITE", "VISIBLE"]
                        segment_count = 1

                        segment1 {
                                start_extent = 0
                                extent_count = 125      # 500 Megabytes

                                type = "striped"
                                stripe_count = 1        # linear

                                stripes = [
                                        "pv0", 381
                                ]
                        }
                }

                vm02swaplv {
                        id = "RrkcHD-SjMW-q4iz-3gGB-kgqV-TPDj-k7Jrl5"
                        status = ["READ", "WRITE", "VISIBLE"]
                        segment_count = 1

                        segment1 {
                                start_extent = 0
                                extent_count = 50       # 200 Megabytes

                                type = "striped"
                                stripe_count = 1        # linear

                                stripes = [
                                        "pv0", 506
                                ]
                        }
                }
        }
}


the 2 other disks are also on the HPT IDE Raid controller ( which is
actualy not running as raid, I just use it for additional IDE ports )

Cris


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