[Lustre-discuss] How smart is Lustre?

[Philippe Weill]

Le 19/12/2012 22:38, Dilger, Andreas a écrit :
> On 2012-12-19, at 11:22, "Allen, Benjamin S"<bsa at lanl.gov<mailto:bsa at lanl.gov>>  wrote:
>
> Hi Jason,
>
> 2. Having two paths to your storage should speed things up. I'm guessing you'd have more than one LUN on the array,
> so you could do something as simple as splitting the LUNs between the two paths, or use round robin to balance the
> traffic between the two paths, etc.
>
> Using round-robin is not a good idea.  This will not increase bandwidth
> (which is already constrained by the disk and bus) but on some RAID controllers
> will cause severe performance impact.
>

I could confirm dell rack disk doesn't support round robin

but you define a prefered controller for each raid volume like this

[root at oss-locean ~]# multipath -ll
LOCEAN_OST5 (3690b11c0000154a40000069a50b86cfb) dm-7 DELL,MD36xxf
[size=22T][features=3 queue_if_no_path pg_init_retries 50][hwhandler=1 rdac][rw]
\_ round-robin 0 [prio=100][active]
  \_ 8:0:0:5  sdn 8:208 [active][ready]
\_ round-robin 0 [prio=0][enabled]
  \_ 7:0:0:5  sdg 8:96  [active][ghost]
LOCEAN_OST4 (3690b11c0000154b50000072350b86892) dm-6 DELL,MD36xxf
[size=22T][features=3 queue_if_no_path pg_init_retries 50][hwhandler=1 rdac][rw]
\_ round-robin 0 [prio=100][active]
  \_ 7:0:0:4  sdf 8:80  [active][ready]
\_ round-robin 0 [prio=0][enabled]
  \_ 8:0:0:4  sdm 8:192 [active][ghost]
LOCEAN_OST3 (3690b11c0000154a40000069750b86cc5) dm-5 DELL,MD36xxf
[size=22T][features=3 queue_if_no_path pg_init_retries 50][hwhandler=1 rdac][rw]
\_ round-robin 0 [prio=100][active]
  \_ 8:0:0:3  sdl 8:176 [active][ready]
\_ round-robin 0 [prio=0][enabled]
  \_ 7:0:0:3  sde 8:64  [active][ghost]
LOCEAN_OST2 (3690b11c0000154b50000072050b86851) dm-4 DELL,MD36xxf
[size=22T][features=3 queue_if_no_path pg_init_retries 50][hwhandler=1 rdac][rw]
\_ round-robin 0 [prio=100][active]
  \_ 7:0:0:2  sdd 8:48  [active][ready]
\_ round-robin 0 [prio=0][enabled]
  \_ 8:0:0:2  sdk 8:160 [active][ghost]
LOCEAN_OST1 (3690b11c0000154a40000069450b86c79) dm-3 DELL,MD36xxf
[size=22T][features=3 queue_if_no_path pg_init_retries 50][hwhandler=1 rdac][rw]
\_ round-robin 0 [prio=100][active]
  \_ 8:0:0:1  sdj 8:144 [active][ready]
\_ round-robin 0 [prio=0][enabled]
  \_ 7:0:0:1  sdc 8:32  [active][ghost]
LOCEAN_OST0 (3690b11c0000154b50000071d50b86052) dm-2 DELL,MD36xxf
[size=22T][features=3 queue_if_no_path pg_init_retries 50][hwhandler=1 rdac][rw]
\_ round-robin 0 [prio=100][active]
  \_ 7:0:0:0  sdb 8:16  [active][ready]
\_ round-robin 0 [prio=0][enabled]
  \_ 8:0:0:0  sdi 8:128 [active][ghost]



> Cheers, Andreas


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