To be sure I redo all tests with adding "conv=fdatasync" to dd :
dd conv=fdatasync if=/dev/zero of=TEST bs=4k count=128000
Results don't really change.
For memory, all my domU have 512Mo of memory.
On dom0, I checked with 200Mo or 4Go free memory, this doesn't change
results.
I adjust dd count parameter to create 512Mo or 8Go file, and have
similar results (there is a small variation of course, about 10%).
I checked also with the Debian Lenny Xen kernel for DomU (so without
ext4), and have same results to.
I really don't think it's a FS issue ; but I suppose the writeback
feature of ext4 avoid this write problems (I didn't try to disable it).
Olivier
DOGUET Emmanuel a écrit :
If you have differences between ext3 and ext4, it can be due to the FS cache?
In your tests what are the memory of dom0 and domU?
Very strange our write problem to RAID harware :/
For my tests, I use "standard" redhat kernel.
Bye.
-----Message d'origine-----
De : xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-
bounces@xxxxxxxxxxxxxxxxxxx] De la part de Olivier B.
Envoyé : mercredi 25 février 2009 20:47
Cc : xen-users
Objet : Re: [Xen-users] Re: Xen Disk I/O performance vs
nativeperformance:XenI/O is definitely super super super slow
I did some tests to on some servers ( time dd if=/dev/zero of=TEST bs=4k
count=512000 )
First server : raid 1 hardware with a PCI 32bits 3ware card.
dom0 (ext3) : 39MB/s
domU (ext3) : 1.4MB/s !!!
domU (ext4) : 40MB/s
Second server : raid 1 software with 2 SATA disks
dom0 (ext3) : 96MB/s
domU (ext3) : 91MB/s
domU (ext4) : 94MB/s
Note : I use vanilla kernel on DomU.
So :
- I see a big write problem from domU on hardware raid
- the writeback feature of ext4 seem to "erase" this problem
Olivier
DOGUET Emmanuel a écrit :
I have finished my tests on 3 servers. On each we loose some bandwidth
with XEN. On our 10 platform ... We always loose some bandwidth, I think
it's normal. Just the bench method who must differ?
I have made bench (write only) between hardware and software RAID under
XEN (see attachment).
Linux Software RAID is always faster than HP Raid. I must try too the
"512MB+Cache Write" option for the HP Raid.
So my problems seem to be here.
-------------------------
HP DL 380
Quad core
-------------------------
Test: dd if=/dev/zero of=TEST bs=4k count=1250000
Hardware Hardware Software Software
RAID 5 RAID 5 RAID 5 RAID 5
4 x 146G 8 x 146G 4 x 146G 8 x 146G
dom0
(1024MB,
1 cpu) 32MB 22MB 88MB (*) 144MB (*)
domU
( 512MB,
1 cpu) 8MB 5MB 34MB 31MB
domU
(4096MB,
2 cpu) -- 7MB 51MB 35MB
*: don't understand this difference.
This performance seems to be good for you?
Best regards.
-----Message d'origine-----
De : DOGUET Emmanuel
Envoyé : mardi 24 février 2009 17:50
À : DOGUET Emmanuel; Fajar A. Nugraha
Cc : xen-users; Joris Dobbelsteen
Objet : RE: [Xen-users] Re: Xen Disk I/O performance vs
nativeperformance:Xen I/O is definitely super super super slow
For resuming :
on RAID 0
dom0: 80MB domU: 56MB Loose: 30M
on RAID1
dom0: 80MB domU: 55 MB Loose: 32%
on RAID5:
dom0: 30MB domU: 9MB Loose: 70%
So loose seem to be "exponantial" ?
-----Message d'origine-----
De : xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] De la part de
DOGUET Emmanuel
Envoyé : mardi 24 février 2009 14:22
À : Fajar A. Nugraha
Cc : xen-users; Joris Dobbelsteen
Objet : RE: [Xen-users] Re: Xen Disk I/O performance vs
nativeperformance:Xen I/O is definitely super super super slow
I have made another test on another server (DL 380)
And same thing!
I'm always use this test :
dd if=/dev/zero of=TEST bs=4k count=1250000
(be careful with memory cache)
TEST WITH 2 RAID 5 (include system on RAID 5, 3x146G + 3x146G)
---------------------------------------------------------------
dom0: 1GO, 1CPU, 2 RAID 5
rootvg(c0d0p1): 4596207616 bytes (4.6 GB)
copied, 158.284 seconds, 29.0 MB/s
datavg(c0d1p1): 5120000000 bytes (5.1 GB)
copied, 155.414 seconds, 32.9 MB/s
domU: 512M, 1CPU on System LVM/RAID5 (rootvg)
5120000000 bytes (5.1 GB) copied, 576.923 seconds, 8.9 MB/s
domU: 512M, 1CPU on DATA LVM/RAID5 (datavg)
5120000000 bytes (5.1 GB) copied, 582.611 seconds, 8.8 MB/s
domU: 512M, 1 CPU on same RAID without LVM
5120000000 bytes (5.1 GB) copied, 808.957 seconds, 6.3 MB/s
TEST WITH RAID 0 (dom0 system on RAID 1)
---------------------------------------
dom0 1GO RAM 1CPU
on system (RAID1):
i3955544064 bytes (4.0 GB) copied, 57.4314 seconds, 68.9 MB/s
on direct HD (RAID 0 of cssiss), no LVM
5120000000 bytes (5.1 GB) copied, 62.5497 seconds, 81.9 MB/s
dom0 4GO RAM 4CPU
domU: 4GO, 4 CPU
on direct HD (RAID 0), no LVM.
5120000000 bytes (5.1 GB) copied, 51.2684 seconds, 99.9 MB/s
domU: 4GO, 4CPU same HD but ONE LVM on it
5120000000 bytes (5.1 GB) copied, 51.5937 seconds, 99.2 MB/s
TEST with only ONE RAID 5 (6 x 146G)
------------------------------------
dom0 : 1024MB - 1CPUI (RHEL 5.3)
5120000000 bytes (5.1 GB) copied, 231.113 seconds, 22.2 MB/s
512MB - 1 CPU
5120000000 bytes (5.1 GB) copied, 1039.42 seconds, 4.9 MB/s
512MB - 1 CPU - ONLY 1 VDB [LVM] (root, no swap)
(too slow ..stopped :P)
4035112960 bytes (4.0 GB) copied, 702.883 seconds, 5.7 MB/s
512MB - 1 CPU - On a file (root, no swap)
1822666752 bytes (1.8 GB) copied, 2753.91 seconds, 662 kB/s
4GB - 2 CPU
5120000000 bytes (5.1 GB) copied, 698.681 seconds, 7.3 MB/s
-----Message d'origine-----
De : Fajar A. Nugraha [mailto:fajar@xxxxxxxxx]
Envoyé : samedi 14 février 2009 06:23
À : DOGUET Emmanuel
Cc : xen-users
Objet : Re: [Xen-users] Re: Xen Disk I/O performance vs native
performance:Xen I/O is definitely super super super slow
2009/2/13 DOGUET Emmanuel <Emmanuel.DOGUET@xxxxxxxx>:
I have mount domU partition on dom0 for testing and it's OK.
But same partiton on domU side is slow.
Strange.
Strange indeed. At least that ruled-out hardware problems :)
Could try with a "simple" domU?
- 1 vcpu
- 512 M memory
- only one vbd
this should isolate whether or not the problem is on your particular
domU (e.g. some config parameter actually make domU slower).
Your config file should have only few lines, like this
memory = "512"
vcpus=1
disk = ['phy:/dev/rootvg/bdd-root,xvda1,w' ]
vif = [ "mac=00:22:64:A1:56:BF,bridge=xenbr0" ]
vfb =['type=vnc']
bootloader="/usr/bin/pygrub"
Regards,
Fajar
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