On 04/09/14 01:50, Sven Oehme wrote:
> Hello everybody,
Hi
> here i come here again, this time to ask some hint about how to
monitor GPFS.
>
> I know about mmpmon, but the issue with its "fs_io_s" and "io_s" is
> that they return number based only on the request done in the
> current host, so i have to run them on all the clients ( over 600
> nodes) so its quite unpractical. Instead i would like to know from
> the servers whats going on, and i came across the vio_s statistics
> wich are less documented and i dont know exacly what they mean.
> There is also this script "/usr/lpp/mmfs/samples/vdisk/viostat" that
> runs VIO_S.
>
> My problems with the output of this command:
> echo "vio_s" | /usr/lpp/mmfs/bin/mmpmon -r 1
>
> mmpmon> mmpmon node 10.7.28.2 name gss01a vio_s OK VIOPS per second
> timestamp: 1409763206/477366
> recovery group: *
> declustered array: *
> vdisk: *
> client reads: 2584229
> client short writes: 55299693
> client medium writes: 190071
> client promoted full track writes: 465145
> client full track writes: 9249
> flushed update writes: 4187708
> flushed promoted full track writes: 123
> migrate operations: 114
> scrub operations: 450590
> log writes: 28509602
>
> it sais "VIOPS per second", but they seem to me just counters as
> every time i re-run the command, the numbers increase by a bit..
> Can anyone confirm if those numbers are counter or if they are OPS/sec.
the numbers are accumulative so everytime you run them they just show
the value since start (or last reset) time.
OK, you confirmed my toughts, thatks
>
> On a closer eye about i dont understand what most of thosevalues
> mean. For example, what exacly are "flushed promoted full track
write" ??
> I tried to find a documentation about this output , but could not
> find any. can anyone point me a link where output of vio_s is explained?
>
> Another thing i dont understand about those numbers is if they are
> just operations, or the number of blocks that was read/write/etc .
its just operations and if i would explain what the numbers mean i
might confuse you even more because this is not what you are really
looking for.
what you are looking for is what the client io's look like on the
Server side, while the VIO layer is the Server side to the disks, so
one lever lower than what you are looking for from what i could read
out of the description above.
No.. what I'm looking its exactly how the disks are busy to keep the
requests. Obviously i'm not looking just that, but I feel the needs to
monitor _*also*_ those things. Ill explain you why.
It happens when our storage is quite busy ( 180Gb/s of read/write ) that
the FS start to be slowin normal /*cd*/ or /*ls*/ requests. This might
be normal, but in those situation i want to know where the bottleneck
is. Is the server CPU? Memory? Network? Spindles? knowing where the
bottlenek is might help me to understand if we can tweak the system a
bit more.
If its the CPU on the servers then there is no much to do beside
replacing or add more servers.If its not the CPU, maybe more memory
would help? Maybe its just the network that filled up? so i can add more
links
Or if we reached the point there the bottleneck its the spindles, then
there is no much point o look somethere else, we just reached the
hardware limit..
Sometimes, it also happens that there is very low IO (10Gb/s ), almost
no cpu usage on the servers but huge slownes ( ls can take 10 seconds).
Why that happens? There is not much data ops , but we think there is a
huge ammount of metadata ops. So what i want to know is if the metadata
vdisks are busy or not. If this is our problem, could some SSD disks
dedicated to metadata help?
In particular im, a bit puzzled with the design of our GSS storage.
Each recovery groups have 3 declustered arrays, and each declustered
aray have 1 data and 1 metadata vdisk, but in the end both metadata and
data vdisks use the same spindles. The problem that, its that I dont
understand if we have a metadata bottleneck there. Maybe some SSD disks
in a dedicated declustered array would perform much better, but this is
just theory. I really would like to be able to monitor IO activities on
the metadata vdisks.
so the Layer you care about is the NSD Server layer, which sits on top
of the VIO layer (which is essentially the SW RAID Layer in GNR)
> I'm asking that because if they are just ops, i don't know how much
> they could be usefull. For example one write operation could eman
> write 1 block or write a file of 100GB. If those are oprations,
> there is a way to have the oupunt in bytes or blocks?
there are multiple ways to get infos on the NSD layer, one would be to
use the dstat plugin (see /usr/lpp/mmfs/sample/util) but thats counts
again.
Counters its not a problem. I can collect them and create some graphs in
a monitoring tool. I will check that.
the alternative option is to use mmdiag --iohist. this shows you a
history of the last X numbers of io operations on either the client or
the server side like on a client :
# mmdiag --iohist
=== mmdiag: iohist ===
I/O history:
I/O start time RW Buf type disk:sectorNum nSec time ms qTime
ms RpcTimes ms Type Device/NSD ID NSD server
--------------- -- ----------- ----------------- ----- -------
-------- ----------------- ---- ------------------ ---------------
14:25:22.169617 R LLIndBlock 1:1075622848 64 13.073
0.000 12.959 0.063 cli C0A70401:53BEEA7F 192.167.4.1
14:25:22.182723 R inode 1:1071252480 8 6.970 0.000
6.908 0.038 cli C0A70401:53BEEA7F 192.167.4.1
14:25:53.659918 R LLIndBlock 1:1081202176 64 8.309
0.000 8.210 0.046 cli C0A70401:53BEEA7F 192.167.4.1
14:25:53.668262 R inode 2:1081373696 8 14.117
0.000 14.032 0.058 cli C0A70402:53BEEA5E 192.167.4.2
14:25:53.682750 R LLIndBlock 1:1065508736 64 9.254
0.000 9.180 0.038 cli C0A70401:53BEEA7F 192.167.4.1
14:25:53.692019 R inode 2:1064356608 8 14.899
0.000 14.847 0.029 cli C0A70402:53BEEA5E 192.167.4.2
14:25:53.707100 R inode 2:1077830152 8 16.499
0.000 16.449 0.025 cli C0A70402:53BEEA5E 192.167.4.2
14:25:53.723788 R LLIndBlock 1:1081202432 64 4.280
0.000 4.203 0.040 cli C0A70401:53BEEA7F 192.167.4.1
14:25:53.728082 R inode 2:1081918976 8 7.760 0.000
7.710 0.027 cli C0A70402:53BEEA5E 192.167.4.2
14:25:57.877416 R metadata 2:678978560 16 13.343 0.000
13.254 0.053 cli C0A70402:53BEEA5E 192.167.4.2
14:25:57.891048 R LLIndBlock 1:1065508608 64 15.491
0.000 15.401 0.058 cli C0A70401:53BEEA7F 192.167.4.1
14:25:57.906556 R inode 2:1083476520 8 11.723
0.000 11.676 0.029 cli C0A70402:53BEEA5E 192.167.4.2
14:25:57.918516 R LLIndBlock 1:1075622720 64 8.062
0.000 8.001 0.032 cli C0A70401:53BEEA7F 192.167.4.1
14:25:57.926592 R inode 1:1076503480 8 8.087 0.000
8.043 0.026 cli C0A70401:53BEEA7F 192.167.4.1
14:25:57.934856 R LLIndBlock 1:1071088512 64 6.572
0.000 6.510 0.033 cli C0A70401:53BEEA7F 192.167.4.1
14:25:57.941441 R inode 2:1069885984 8 11.686
0.000 11.641 0.024 cli C0A70402:53BEEA5E 192.167.4.2
14:25:57.953294 R inode 2:1083476936 8 8.951 0.000
8.912 0.021 cli C0A70402:53BEEA5E 192.167.4.2
14:25:57.965475 R inode 1:1076503504 8 0.477 0.000
0.053 0.000 cli C0A70401:53BEEA7F 192.167.4.1
14:25:57.965755 R inode 2:1083476488 8 0.410 0.000
0.061 0.321 cli C0A70402:53BEEA5E 192.167.4.2
14:25:57.965787 R inode 2:1083476512 8 0.439 0.000
0.053 0.342 cli C0A70402:53BEEA5E 192.167.4.2
you basically see if its a inode , data block , what size it has (in
sectors) , which nsd server you did send this request to, etc.
on the Server side you see the type , which physical disk it goes to
and also what size of disk i/o it causes like :
14:26:50.129995 R inode 12:3211886376 64 14.261
0.000 0.000 0.000 pd sdis
14:26:50.137102 R inode 19:3003969520 64 9.004
0.000 0.000 0.000 pd sdad
14:26:50.136116 R inode 55:3591710992 64 11.057
0.000 0.000 0.000 pd sdoh
14:26:50.141510 R inode 21:3066810504 64 5.909
0.000 0.000 0.000 pd sdaf
14:26:50.130529 R inode 89:2962370072 64 17.437
0.000 0.000 0.000 pd sddi
14:26:50.131063 R inode 78:1889457000 64 17.062
0.000 0.000 0.000 pd sdsj
14:26:50.143403 R inode 36:3323035688 64 4.807
0.000 0.000 0.000 pd sdmw
14:26:50.131044 R inode 37:2513579736 128 17.181
0.000 0.000 0.000 pd sddv
14:26:50.138181 R inode 72:3868810400 64 10.951
0.000 0.000 0.000 pd sdbz
14:26:50.138188 R inode 131:2443484784 128 11.792
0.000 0.000 0.000 pd sdug
14:26:50.138003 R inode 102:3696843872 64 11.994
0.000 0.000 0.000 pd sdgp
14:26:50.137099 R inode 145:3370922504 64 13.225
0.000 0.000 0.000 pd sdmi
14:26:50.141576 R inode 62:2668579904 64 9.313
0.000 0.000 0.000 pd sdou
14:26:50.134689 R inode 159:2786164648 64 16.577
0.000 0.000 0.000 pd sdpq
14:26:50.145034 R inode 34:2097217320 64 7.409
0.000 0.000 0.000 pd sdmt
14:26:50.138140 R inode 139:2831038792 64 14.898
0.000 0.000 0.000 pd sdlw
14:26:50.130954 R inode 164:282120312 64 22.274
0.000 0.000 0.000 pd sdzd
14:26:50.137038 R inode 41:3421909608 64 16.314
0.000 0.000 0.000 pd sdef
14:26:50.137606 R inode 104:1870962416 64 16.644
0.000 0.000 0.000 pd sdgx
14:26:50.141306 R inode 65:2276184264 64 16.593
0.000 0.000 0.000 pd sdrk
mmdiag --iohist its another think i looked at it, but i could not find
good explanation for all the "buf type" ( third column )
allocSeg
data
iallocSeg
indBlock
inode
LLIndBlock
logData
logDesc
logWrap
metadata
vdiskAULog
vdiskBuf
vdiskFWLog
vdiskMDLog
vdiskMeta
vdiskRGDesc
If i want to monifor metadata operation whan should i look at? just the
metadata flag or also inode? this command takes also long to run,
especially if i run it a second time it hangs for a lot before to rerun
again, so i'm not sure that run it every 30secs or minute its viable,
but i will look also into that. THere is any documentation that descibes
clearly the whole output? what i found its quite generic and don't go
into details...
>
> Last but not least.. and this is what i really would like to
> accomplish, i would to be able to monitor the latency of metadata
operations.
you can't do this on the server side as you don't know how much time
you spend on the client , network or anything between the app and the
physical disk, so you can only reliably look at this from the client,
the iohist output only shows you the Server disk i/o processing time,
but that can be a fraction of the overall time (in other cases this
obviously can also be the dominant part depending on your workload).
the easiest way on the client is to run
mmfsadm vfsstats enable
from now on vfs stats are collected until you restart GPFS.
then run :
vfs statistics currently enabled
started at: Fri Aug 29 13:15:05.380 2014
duration: 448446.970 sec
name calls time per call total time
-------------------- -------- -------------- --------------
statfs 9 0.000002 0.000021
startIO 246191176 0.005853 1441049.976740
to dump what ever you collected so far on this node.
We already do that, but as I said, I want to check specifically how gss
servers are keeping the requests to identify or exlude server side
bottlenecks.
Thanks for your help, you gave me definitely few things where to look at.
Salvatore
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