Eep no, that 5% aggr snapshot space is really important in metros.
On 26 March 2016 at 14:48, Klise, Steve Steve.Klise@wwt.com wrote:
Lame question, but if the aggr is at standard 5% snapshot reserve, maybe freeing up that space may help (setting to 0)..
Thanks
Steve Klise
From: toasters-bounces@teaparty.net on behalf of Jeffrey Mohler < jmohler@yahoo-inc.com> Reply-To: Jeffrey Mohler jmohler@yahoo-inc.com Date: Friday, March 25, 2016 at 7:23 PM To: "Flores, Paul" Paul.Flores@netapp.com, josef radinger < cheese@nosuchhost.net> Cc: "toasters@teaparty.net" toasters@teaparty.net Subject: Re: metro under high latency
Ya...I wouldn't get near reallocation that you really =dont= need, given the CPU and disk use, and secondary effects that will add to your system.
Free space frag is only an issue, if it's an issue...and disk that 'not-busy' is soaking up the additional IO from it cleanly, and without any of the other secondary effects of fixing a problem that ain't there.
Work on the actual problem. Alignment...if it does exist as an issue, it chews up CPU, chews up disk IO, and makes the CP process slow and latent to client ACKs.
Jeff Mohler jmohler@yahoo-inc.com Tech Yahoo, Storage Architect, Principal (831)454-6712 YPAC Gold Member Twitter: @PrincipalYahoo CorpIM: Hipchat & Iris
On Friday, March 25, 2016 6:49 PM, "Flores, Paul" Paul.Flores@netapp.com wrote:
Josef,
If you want to figure out if you are suffering from overhead from a lack of contagious freespace, you can compute it from statit with the following formula:
(CP Reads * chain) / (writes * chain) = CPRead Ratio. This can be done on any data disk in a raid group.
this will give you a value expressing the amount of correct parity(CP Read) workload vs write workload. below .5 is very efficientŠ .51 - .75 is usually not noticeable, but may need some attentionŠ .75 - 1 is bad, and more than 1 is _very_ badŠ Generally, the closer the ratio gets to 1:1 the less efficient the controller is, because it¹s having to do so much CP Read IO for a given write stripe.
The ratio has been steadily climbing since januaryŠ (see default.png attachment for chart). Is there a new type of workload on the system that is either quickly filling the aggr, or has a _lot_ of add and delete characteristics to it (creating lots of holes in the stripes), but even so, I¹d be surprised to see it affecting write latency on it¹s own this early in the game. it¹s usually got to be a bit higher before anyone notices, but there is no denying, there does seem to be some correlation with the latency increases on your VM Volumes as the ratio gets worseŠ
you will want your aggr option for free_space_realloc=on, I think, if you want to ensure that free space stays happy for the future. TR-3929 ŒReallocate Best Practices Guide¹ has all the gory details.
you may also want to take a peak at nfs-stat -d on your controllerŠ there are some indications of VMDK files that may not be aligned properly, and checking the last couple of months, there were a few spots where the controller ran out of partial write handling resourcesŠ probably not the overall issue, but Œone more thing¹ to be concerned with.
Paul Flores Professional Services Consultant 3 Americas Performance Assessments Team NetApp 281-857-6981 Direct Phone 713-446-5219 Mobile Phone paul.flores@netapp.com
http://www.netapp.com/us/solutions/professional/assessment.html
On 3/25/16, 3:29 PM, "toasters-bounces@teaparty.net on behalf of josef radinger" <toasters-bounces@teaparty.net on behalf of cheese@nosuchhost.net> wrote:
cpu on netapp is higher than it used to be. i think we see higher cpu than normal since around 1 month. we used to be at 30-40% and now we are slightly higher during work-hours at 50-60% with some peaks to around 90%. i'm currently not in my office and have no access to exact statistics.
On Fri, 2016-03-25 at 19:41 +0000, Jeffrey Mohler wrote:
They should be 100% on an empty aggregate..but still, spindles seem to handle the workload just fine.
What the history of CPU on the system..when did it work well last, what was CPU load then?
Jeff Mohler Tech Yahoo, Storage Architect, Principal (831)454-6712 YPAC Gold Member Twitter: @PrincipalYahoo CorpIM: Hipchat & Iris
On Friday, March 25, 2016 12:28 PM, josef radinger <cheese@nosuchhost .net> wrote:
performance advisor shows the following: read latency on a vmware-datastore at around 5-20ms. write latency at around 10-15ms with peaks: "other" latency at up to 500ms, i'm quite sure this other is my problem.
but what me bothers is the stripe ratio: 2428.65 partial stripes 85.83 full stripes my knowledge is that i should have a lot more full stripes than partial ones.
images are at http://www.nosuchhost.net/~cheese/temp/readandwrite.png http://www.nosuchhost.net/~cheese/temp/other.png
my colleagues had troubles while patching several windows-systems residing in that datastore, as the systems got unresponsive and access got very slow.
On Fri, 2016-03-25 at 18:42 +0000, Jeffrey Mohler wrote:
Are you write latency troubled, or read latency troubled?
I don't see free space frag as a huge issue, as lightly loaded as the spindles report to be.
Jeff Mohler Tech Yahoo, Storage Architect, Principal (831)454-6712 YPAC Gold Member Twitter: @PrincipalYahoo CorpIM: Hipchat & Iris
On Friday, March 25, 2016 11:37 AM, josef radinger <cheese@nosuchho st.net> wrote:
hi
i have a metro cluster (rather old) which is currently responding very slowly. 7-mode 8.1.4
there is only one aggregate per head, filled at around 72% one one head and 79% on the other head. attached is a statit and sysstat -x 1 from one head.
i see lots of partial stripes and only several full stripes. i assume this should mean not enough free space, which should imho not be a problem at my aggregates.
what is the correct procedure for performing a free space reallocation? i did:
- stop all volume-reallocates
- disable read_reallocation on all volumes
- raid.lost_write.enable off
- aggr options aggr0 resyncsnaptime 5
- reallocate start -A -o aggr0
- wait for finish of reallocate
- aggr options aggr0 resyncsnaptime 60
- enable read_reallocation on all volumes
- reenable all volume-level reallocates
my aggregates have options:
aggr options aggr0 root, diskroot, nosnap=off, raidtype=raid_dp, raidsize=20, ignore_inconsistent=off, snapmirrored=off, resyncsnaptime=60, fs_size_fixed=off, snapshot_autodelete=on, lost_write_protect=on, ha_policy=cfo, hybrid_enabled=off, percent_snapshot_space=5%, free_space_realloc=off
any advice? josef
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