[DRBD-user] Slow Reads on VM - Xenserver and DRBD

Christian Balzer chibi at gol.com
Wed Jul 25 02:56:46 CEST 2012

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

On Tue, 24 Jul 2012 14:08:29 +0200 Phil Stricker wrote:

> Hi!
> One Problem is solved:
> The extremely bad read-performance in the VM is gone away after the
> downgrade from DRBD 8.4.1 to 8.3.13!!
Ah yes, 8.4... ^o^

> There is just one problem left:
> The setup "xenserver <-> LSI9260 <-> 8x SSD" is too slow! I can just get
> about 450 MB/s - no matter, if i set it up as an Raid 10 or Raid 0!
This is xenserver directly talking to the RAID device, not DRBD?
> Did you ever see something like that?
Not using xenserver, but that now really looks like a xenserver limitation.

This is what I get on an Adaptec 51645 with an 8 disk RAID10 of 2TB SATA
Hitachi drives (bonnie++):
 3.2, 8disk R10, ext4, 1G journal
Version  1.96       ------Sequential Output------ --Sequential Input- --Random-
Concurrency   1     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
mb13            64G           529030  55 270813  33           1072430  63 642.0  50

So the writes on this setup with inferior drives are faster than your reads
and reads are twice as fast...


Christian Balzer        Network/Systems Engineer                
chibi at gol.com   	Global OnLine Japan/Fusion Communications

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