Hmm, interesting question. I am curious to see what the results are.
It sounds like you ruled out that it could be reads from some other operation like such as:
Snapmirror/snapvault
Sync /semi-sync snapmirror
Raid scrub
Wafl scan
Reallocation
Another thought, not sure if fragmentation could cause that behavior, but do you have a very full aggregate?
-JMS
From: toasters-bounces@teaparty.net [mailto:toasters-bounces@teaparty.net] On Behalf Of Alon Zeltser
Sent: Monday, October 21, 2013 10:28 AM
To: toasters@teaparty.net
Subject: unexplained read operation
Hello toasters
I encounter rather strange situation
I have a system FAS2040 with 1 aggr of 23x450g raid group ontap version 8.1.3p2
Every write operation being generated on this aggregate automatically caused a read operation
When I try to create 100% sequential write operation using tools such as sio_ntap or filersio
Instead of the expected 150Mb throughput I get 100MB write and 50MB read
On another FAS2040 system using the same commands I get 100% write and no reads
As you can see
filersio asyncio_active 0 -r 0 64k 0 15g 60 1 /vol/test/testfile
CPU NFS CIFS HTTP Total Net kB/s Disk kB/s Tape kB/s Cache Cache CP CP Disk OTHER FCP iSCSI FCP kB/s iSCSI kB/s
93% 0 0 0 5 26 1 24242 118671 0 0 0s 99% 72% Fn 43% 0 0 5 0 0 24 0
90% 0 0 0 4 4 1 40959 102501 0 0 19 100% 89% Fn 43% 1 0 3 0 0 2 0
86% 0 0 0 3 3 1 23126 125022 0 0 0s 99% 69% : 59% 0 0 3 0 0 2 0
93% 0 0 0 7 1 1 28200 135740 0 0 0s 99% 97% Ff 48% 7 0 0 0 0 0 0
92% 0 0 0 6 15 1 48764 115324 0 0 0s 99% 91% Ff 52% 0 0 6 0 0 14 0
90% 0 0 0 6 16 1 36148 156492 0 0 0s 99% 83% Ff 56% 0 0 6 0 0 14 0
95% 0 0 0 0 4 4 32784 114555 0 0 0s 99% 77% Fs 48% 0 0 0 0 0 0 0
92% 0 0 0 18 90 12 34931 104059 0 0 0s 99% 88% Fn 42% 0 0 18 0 0 79 0
88% 0 0 0 8 3 1 20463 124800 0 0 0s 100% 83% Fn 45% 5 0 3 0 0 2 0
89% 0 0 0 2 2 1 34050 112166 0 0 0s 99% 87% Fn 44% 0 0 2 0 0 1 0
92% 0 0 0 3 7 1 33025 112816 0 0 0s 99% 88% Fn 46% 0 0 3 0 0 5 0
91% 0 0 0 3 3 1 30929 130833 0 0 0s 100% 73% : 50% 0 0 3 0 0 2 0
92% 0 0 0 7 24 2 36484 134260 0 0 0s 100% 98% Ff 50% 0 0 7 0 0 22 0
86% 0 0 0 6 1 1 38608 125140 0 0 0s 99% 90% Ff 44% 5 0 1 0 0 1 0
93% 0 0 0 4 3 1 28748 104544 0 0 0s 100% 75% Ff 43% 0 0 4 0 0 2 0
87% 0 0 0 5 18 1 28128 158608 0 0 0s 100% 90% Fs 55% 0 0 5 0 0 17 0
93% 0 0 0 2 3 34 33115 104980 0 0 0s 99% 85% Fn 41% 0 0 2 0 0 1 32
84% 0 0 0 5 28 7 37185 109425 0 0 0s 100% 78% Fn 48% 0 0 5 0 0 21 0
91% 0 0 0 9 3 1 30224 118322 0 0 0s 99% 97% Fn 47% 7 0 2 0 0 1 0
89% 0 0 0 2 3 4 27649 118335 0 0 0s 99% 88% : 45% 0 0 2 0 0 1 0
CPU NFS CIFS HTTP Total Net kB/s Disk kB/s Tape kB/s Cache Cache CP CP Disk OTHER FCP iSCSI FCP kB/s iSCSI kB/s
in out read write read write age hit time ty util in out in out
88% 0 0 0 14 57 39 43284 133480 0 0 0s 100% 98% Ff 50% 0 0 14 0 0 52 0
92% 0 0 0 2 6 16 47936 109432 0 0 0s 99% 86% Ff 46% 0 0 2 0 0 1 0
88% 0 0 0 23 86 3 45340 141014 0 0 0s 99% 73% Ff 55% 3 0 20 0 0 82 0
92% 0 0 0 10 5 4 21787 123980 0 0 0s 99% 80% Fn 44% 7 0 3 0 0 1 0
95% 0 0 0 2 4 3 34751 98158 0 0 0s 99% 82% Fn 44% 0 0 2 0 0 1 0
91% 0 0 0 1 3 1 35022 118549 0 0 0s 100% 60% Fn 48% 0 0 1 0 0 0 0
92% 0 0 0 87 3 1 25455 123066 0 0 0s 100% 80% Fn 47% 84 0 3 0 0 1 0
83% 0 0 0 8 32 2 36956 121303 0 0 0s 100% 88% : 46% 0 0 8 0 0 30 0
85% 0 0 0 5 2 1 62064 140088 0 0 0s 100% 92% Ff 59% 5 0 0 0 0 0 0
95% 0 0 0 3 3 1 39352 117364 0 0 0s 99% 71% Ff 48% 0 0 3 0 0 2 0
94% 0 0 0 3 3 1 42008 136943 0 0 0s 99% 94% Fs 53% 0 0 3 0 0 2 0
92% 0 0 0 0 2 7 26147 111286 0 0 0s 99% 58% Fn 44% 0 0 0 0 0 0 0
90% 0 0 0 3 3 1 29567 110665 0 0 20 99% 87% Fn 44% 0 0 3 0 0 1 0
90% 0 0 0 9 4 1 40031 111273 0 0 16 99% 86% Fn 43% 5 0 4 0 0 2 0
84% 0 0 0 0 1 1 36760 105709 0 0 0s 100% 84% Fn 43% 0 0 0 0 0 0 0
92% 0 0 0 3 3 1 31033 137891 0 0 0s 100% 99% : 53% 0 0 3 0 0 2 0
83% 0 0 0 4 6 1 32991 140148 0 0 0s 100% 89% F 51% 0 0 4 0 0 5 0
Any thoughts why this could happens ?
Nothing else is running on this netapp except for this test
Thanks
Alon Z
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