Tomasz Chmielewski wrote: > 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 > > Hmmm, perhaps for iSCSI. But using fibre SAN, I saturate my 2Gbps link (almost 200MB/sec). -- Chris Cox Sr. Unix Sys Admin _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
