[DRBD-user] playing around with blockdev --setra

Rudolph Bott rb at megabit.net
Thu Jan 10 13:58:57 CET 2008

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Hey list,

did anybody of you guys recently play around with the blockdev --setra command? My setup (software-raid/drbd/lvm/iscsi/xen) is rather complex stacked and I was wondering if I am able to gain a performance boost at all here. Would I have to apply the "blockdev --setra xy" to all of the involved 
physical devices?
blockdev --setra 1024 /dev/sd[a-d]
blockdev --setra 1024 /dev/md3
blockdev --setra 1024 /dev/vg_storage/volume

(well and also on the iscsi blockdevice on the xen server AND on the virtual device inside the xen DomU..?)

The only block device I did not touch at all was /dev/drbd0 because it already had a non-standard setting (786 in my case)

Comparing the bonnie results, setting the read-ahead value on some or all of the above mentioned did not change much (values varied by 1-4mb/sec)

Mit freundlichen Grüßen / with kind regards

Rudolph Bott
Megabit Informationstechnik GmbH
Karstr.25  41068 Moenchengladbach  Tel:02161/30898-0  Fax:-18
AG MG HRB 10141, GF: Dipl.-Ing. Thomas Tillig, Michael Benten

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