Chris Cox schrieb:
Joseph L. Casale wrote:
Hi,
I am wanting to use LVM behind an iet iscsi target and I am wondering
how much overhead if any does LVM add? Would the performance degrade
any, currently I am exporting full unpartitioned discs and am happy with
the performance. From what I am reading now, I would likely partition
the physical discs and use that in LVM then export a volume.
Overhead is negligible. I haven't seen any impact at all.
Quite the contrary - unless the default settings are not changed.
By default, the readahead values for LVM volumes is quite low / for
iSCSI, I always have to change it to get acceptable performance (one
might want to replace the $HOSTNAME with the name of the PV, or define a
separate list; "setra" values might need some experimenting, too):
LVMS=$(/bin/ls /dev/$HOSTNAME/)
for LVM in $LVMS
do
blockdev --setra 16384 /dev/$HOSTNAME/$LVM
done
--
Tomasz Chmielewski
http://blog.wpkg.org
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