Hi Rene,
Rene Zbinden wrote:
hello
has someone experience with installing gentoo on a san attached disk
with mulitpath support? if someone can give me some hints, I would
appreciate that.
thanks in advance
rene
I have tested multipath-tools from
http://christophe.varoqui.free.fr/wiki/wakka.php?wiki=Home
during the past three weeks and send some messages to the dm-devel mailing
list. Here is a summary:
I.) ***** Installation *****
http://christophe.varoqui.free.fr/wiki/wakka.php?wiki=QuickInstallGuide
emerge multipath-tools
II.) ***** Configuration *****
1.) load dm-mapper and HBA kernel modules. lower HBA timeouts (see FAQ).
2.) create partitions on each lun (e.g.: lun0 has two paths sda and sdb -
"fdisk sda" creates the partitions for sda _and_ sdb) - you have to do this
step _before_ creating multipath devices (kpartx in
/etc/dev.d/block/multipath.dev reads this partition information)
3.) create /etc/multipath.conf
- check multipath.conf.annotated and multipath.conf.synthetic in the
multipath-tools tarball
- get lun wwid's with "scsi_id -g -u -s /block/sd?"
- create a "multipath { ... }" section for each lun (define "wwid" and "alias")
- create a "device { ... }" section for your storage (see "TestedEnvironments"
located at the multipath-tools homepage) - set "path_grouping_policy" and
"prio_callout" (setting "prio_callout" is important. if you choose a wrong
value, you will see nothing after starting multipath)
4.) start multipathd (debug with "-d" or "-v4" (syslog))
Note: multipathd doesn't work with my hardware (I am using HP DL380, EVA 3000
HSV100). But the daemon isn't needed necessarily:
My question at the dm-devel mailing list:
>> ===> Multipathing seems to work without but not with multipathd.
>> [...] Does I really need multipathd? I suppose so :-)
>>
And the answer from christophe varoqui (multipath-tools developer):
> multipathd is needed to reinstate paths.
> In your case the rport disappears and reappears so the mecanism is all
> hotplug-driven and thus may work without the daemon ... if memory
> ressources permits hotplug and multipath(8) execution, that is.
Nicola (see below) has an EMC CX 300 storage system and uses multipathd
without problems.
5.) run "multipath /dev/sd?" for each sd? device
multipath should create device-mapper table entries (see "dmsetup table"),
block-device-files in /dev/mapper/ and links in /dev/ for the lun and for each
partition
e.g.: you have created two partitions and your lun alias is "yellow" (defined
in /etc/multipath.conf):
# dmsetup table
yellow1: ...
yellow: ...
yellow2: ...
# ls /dev/mapper/
yellow yellow1 yellow2 control
# ls -F /dev/yellow*
/dev/yellow@ /dev/yellow1@ /dev/yellow2@
and check "multipath [-v3] -ll"
6.) create filesystems and mount /dev/yellow1 and /dev/yellow2
you can delete the current configuration with "dmsetup remove yellow2; dmsetup
remove yellow1; dmsetup remove yellow"
III.) ***** Test *****
I tested the multipath environment with a little perl script and a mysql
database:
My trafficmaker-host executed this script 27 times (parallel):
...
for(my $count=1;$count<=1000000;$count++)
{
...
my $sql="INSERT INTO $table VALUES($id,\"$value\")";
my $return=$dbh->do($sql);
...
}
...
{
my $sql="SELECT COUNT(*) FROM $table WHERE id=$id";
my $sth=$dbh->prepare($sql);
my $return=$sth->execute();
...
$selectCount=$sth->fetchrow_array();
...;
}
The database host had to insert this 30 byte strings and I have started some
copy-jobs (cp -a /usr/* /partition_mounted_with_multipath/ etc.) to increase
the I/O load. During this test I have disabled and enabled the different
HBA-Switch-Ports with the following result: It took 6 to 15 seconds before
"multipath -l" showed that a path is down (15 seconds because the host had a
30.0 CPU load and responded very slowly), but no INSERT got lost :-)))
IV.) ***** More Documentation *****
Check the homepage (I will add more documentation and helper scripts in the
next days) and the dm-devel mailing list archive:
https://www.redhat.com/mailman/listinfo/dm-devel
E.g. Nicola Murino posted his experience with an EMC storage controller. He is
using Gentoo too.
Hope that helps
Simon
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