German
There isn’t really a best option at the moment, although if your IO sizes aren’t that big, 4.0+ is probably the best option.
From: German Anders [mailto:ganders@xxxxxxxxxxxx]
Sent: 24 June 2015 16:02
To: Nick Fisk
Cc: ceph-users
Subject: Re: kernel 3.18 io bottlenecks?
Thanks a lot Nick, ok i see, and is there any lower version that could be used? Or is best to go with 4.0+ ?
German
2015-06-24 11:55 GMT-03:00 Nick Fisk <nick@xxxxxxxxxx>:
That kernel probably has the bug where tcp_nodelay is not enabled. That is fixed in Kernel 4.0+, however also in 4.0 blk-mq was introduced which brings two other limitations:-
1. Max queue depth of 128
2. IO’s sizes are restricted/split to 128kb
From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of German Anders
Sent: 24 June 2015 15:45
To: ceph-users
Subject: kernel 3.18 io bottlenecks?
Hi all,
Is there any IO botleneck reported on kernel 3.18.3-031803-generic? since I'm having a lot of iowait and the cluster is really getting slow, and actually there's no much going on. I've read some time ago that there were some issues with kern 3.18, so I would like to know what's the 'best' kernel to go with, I'm using Ubuntu 14.04.1LTs and Ceph v0.82.
Thanks a lot,
Best regards,
German
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