Hello.
I have three Dell 2950 servers - two Xen machines - xen01 and xen02 -
and one that is used to store backups. Each server has a pair of l quad
core CPU''s, the same SAS disk drives and firmware versions (BIOS, SCSI
controller, onboard NIC and BMC). The only way that they differ is that
one server (xen01) currently has 12GB of RAM while the other 2 have 16GB
of RAM.
With regards to the software that is installed on xen01 and xen02:
OS: CentOS 5.5 64 bit
kernel: 2.6.18-194.17.1.el5xen
xen version: 3.0.3.105.el5_5.5
So with regards to xen01: It currently has 3 paravirtualized (PV)
guests on it with each guest running CentOS 4.8 32 bit and Xen kernel
version:
kernel-xenU-2.6.9-100
Now, with regards to file transfer speeds on the xen01 host and its guests:
xen01
====Dom0 <- backup server: 30MB/s
DomU (any) <- backup server: 30MB/s
DomU (any) <- DomU (any) 30MB/s
DomU (any) <- Dom0 23MB/s
So no problems there.
Now, xen02 currently has two PV guests on it: A CentOS 4.8 32 bit guest
and a CentOS 5.5 64 bit guest and so with regards to file transfer
speeds for the xen02 host and its guests:
xen02
====Dom0 <- backup server: 30MB/s
DomU (CentOS 4) <- backup server: 4MB/s
DomU (CentOS 5) <- backup server: 23MB/s
DomU (CentOS 5) <- DomU (CentOS 4) 23MB/s
DomU (CentOS 4) <- DomU (CentOS 5) 4MB/s
DomU (CentOS 5) <- DomU (CentOS 4) 23MB/s
DomU (CentOS 4) <- Dom0 23MB/s
DomU (CentOS 5) <- Dom0 30MB/s
Now the obvious problem here is the CentOS 4 guest on xen02. The
difference between the three CentOS 4 guests on xen01 and the CentOS 4
guest on xen02 is that the three guests on xen01 each started off as
separate machines and were upgraded over the years from CentOS 4.2 to
CentOS 4.8. So not too long ago, we decided to decommission those three
old servers (the hardware that is) and so performed a bare metal restore
of each three of those servers from the backup server to xen01.
However, in the case of the CentOS 4 guest on xen02: It was simply being
created and installed as a CentOS 4.8 guest straight onto xen02 (using
virt-install).
Other things that I have checked are that all software versions and
firmware are the same between both servers and that the output of :
ifconfig -a
brctl show
(ignoring the different MAC and IP addresses of course) are the same
when comparing xen01 and xen02 and are the same when comparing between
the CentOS 4 guests and that:
/etc/sysconfig/network-scripts/{ifcfg-eth0,ifcfg-eth1}
/etc/sysconfig/hw.conf
/etc/sysconfig/network
/etc/modprobe.conf
/etc/xen/*
are identical when comparing between both xen01 and xen02 and are also
identical when comparing between the CentOS 4 guests (except for the MAC
and IP addresses of copurse), I am totally at a loss here as to why the
CentOS 4 guest on xen02 has such atrociously low speeds when
transferring files from the backup server (and also from the CentOS 5
guest on the same server - but I don''t really care about that other
than
it may provide some sort of clue).
Another clue is that if I boot a Rescue CD such as the latest version of
R.I.P. Linux where HVM has to be used, the transfer speed from the
backup server to the R.I.P. Linux guest is also a paltry 4MB/s.
So if anyone can provide me with some clues or information as to how to
improve on this 4MB/s speed problem both with the CentOS 4 container as
well as with the rescue CD, then I would be most grateful as this
problem has been driving me nuts.
Cheers,
Mike.
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