Re: RBD+KVM problems with sequential read

[Daniel Schwager <Daniel.Schwager@xxxxxxxx>]

setup a bitter value for read_ahead_kb ? I tested with 256 MB read ahead cache (

 

 

 

From: ceph-users-bounces@xxxxxxxxxxxxxx [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of ???? ???????
Sent: Friday, February 07, 2014 10:55 AM
To: Konrad Gutkowski
Cc: ceph-users@xxxxxxxxxxxxxx
Subject: Re: [ceph-users] RBD+KVM problems with sequential read

 

echo "noop">/sys/block/vda/queue/scheduler 

echo "1000" >/sys/block/vda/queue/nr_requests

echo "8192">/sys/block/vda/queue/read_ahead_kb

 

 

[root@nfs tmp]# dd if=test of=/dev/null

39062500+0 records in

39062500+0 records out

20000000000 bytes (20 GB) copied, 244.024 s, 82.0 MB/s

 

Changing these parameters are not affected...

Are there other ideas on this problem? 

Thank you.

 

 

2014-02-07 Konrad Gutkowski <konrad.gutkowski@xxxxxx>:

Hi,

 

W dniu 07.02.2014 o 08:14 Ирек Фасихов <malmyzh@xxxxxxxxx> pisze:

 

[...]

 

Why might such a low speed sequential read? Do ideas on this issue?

 

Iirc you need to set your readahead for the device higher (inside the vm) to compensate for network rtt.

blockdev --setra x /dev/vda

 

 

Thanks.

 

 

-- 

С уважением, Фасихов Ирек Нургаязович

Моб.: +79229045757

 

Regards,

Konrad Gutkowski

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--

С уважением, Фасихов Ирек Нургаязович

Моб.: +79229045757

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