[OpenAFS] OpenAFS speed
Nathan Ward
nward@esphion.com
Wed, 25 Jun 2003 08:53:47 +1200
On Tue, 24 Jun 2003 16:25:50 -0400 (EDT), Derrick J Brashear
<shadow@dementia.org> wrote:
> On Wed, 25 Jun 2003, Nathan Ward wrote:
>
>> Several times I have mentioned this and gotten no useful response that I
>> can remember.
>>
>> I am running OpenAFS on linux machines. Take a look at the context
>> switches
>> on the client and the server....
>>
>> (vmstat 1, look at the "cs" column)
>>
>> NFS solves this problem by having a fully kernel server and client.
>
> Our client is fully kernel, and yet it's the client that people seem to
> indicate is the big problem.
One moment please...
AFS server on serv-1, client is serv-2. Gigabit ethernet between them...
nward@serv-2:/$ vmstat 1
procs memory swap io system
cpu
r b w swpd free buff cache si so bi bo in cs us sy
id
0 0 0 576 349032 37444 389620 0 0 1 2 18 11 0 0
6
0 0 0 576 282320 37512 456188 0 0 0 0 268 2707 0 24
76
0 0 0 576 282320 37512 456188 0 0 0 0 876 14909 0 43
57
0 0 0 576 282320 37512 456188 0 0 0 0 881 14884 0 40
60
0 0 0 576 282320 37512 456188 0 0 0 0 865 14917 1 44
55
0 0 0 576 282320 37512 456188 0 0 0 0 846 15008 0 39
61
1 0 0 576 254496 37596 483928 0 0 0 128 713 12035 0 44
56
0 0 2 576 238196 37612 500208 0 0 0 0 687 13162 0 43
57
0 0 2 576 238196 37612 500208 0 0 0 8 821 14754 0 43
57
0 0 1 576 238196 37612 500208 0 0 0 0 854 14737 0 39
61
0 0 1 576 238196 37612 500208 0 0 0 8 846 14696 0 45
55
0 0 0 576 238196 37612 500208 0 0 0 0 777 13821 0 34
65
0 0 0 576 238264 37612 500208 0 0 0 0 238 2982 0 6
93
0 0 0 576 238264 37612 500208 0 0 0 0 103 116 0 0
100
0 0 0 576 238264 37612 500208 0 0 0 0 103 114 0 0
100
serv-1:~# vmstat 1
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu--
--
r b swpd free buff cache si so bi bo in cs us sy id
wa
0 0 4452 234396 84868 308172 0 0 1 14 10 6 0 1 99
0
0 0 4452 234388 84868 308172 0 0 0 0 120 45 0 0
100 0
0 0 4452 234388 84868 308172 0 0 0 0 125 56 0 0
100 0
0 0 4452 299904 84884 242636 0 0 0 40 114 54 0 3 97
0
1 0 4452 293592 84892 248844 0 0 0 0 2193 1944 40 12 49
0
1 0 4452 287040 84900 255388 0 0 0 0 2287 1994 45 12 44
0
1 0 4452 280476 84904 261948 0 0 0 0 2266 1838 47 12 42
0
1 0 4452 273932 84916 268476 0 0 0 0 2207 1891 41 12 47
0
1 0 4452 268280 84920 274124 0 0 0 260 2050 1724 37 14 50
0
1 0 4452 263988 84924 278412 0 0 0 0 1494 1231 28 7 64
0
1 0 4452 257436 84932 284956 0 0 0 0 2233 2050 47 9 44
0
2 0 4452 250884 84940 291500 0 0 0 0 2260 1823 48 10 42
0
1 0 4452 244320 84944 298060 0 0 0 0 2251 1922 43 14 43
0
1 0 4452 238168 84952 304204 0 0 0 168 2132 1857 41 10 49
0
0 0 4452 234196 84956 308172 0 0 0 0 1361 1150 25 8 66
0
0 0 4452 234196 84956 308172 0 0 0 0 127 60 0 0
100 0
nward@serv-2:/$ dd if=/dev/zero of=/afs/alb-nz/public/blah bs=256k
count=256 256+0 records in
256+0 records out
With a client machine with 100Mbit ethernet, the context switches are
roughly halfed, with the speed being roughly halved also.
I am using a disk based cache for these machines. I'll try again with a
ramdisk and report back.
>> People claim that "OpenAFS scales better", sure it definately does, but
>> should this mean that it's maximum speed is degraded? I don't see how
>> this
>> can be..?
>
> I don't think it should, or that it does. I think it's incidental.
Right, my point here is that people use it as an excuse, as though its slow
because its scalable.
--
Nathan Ward
Esphion Ltd.