I am not sure that's really true. ALL writes are going to be "sequential" if they can - the filer writes to NVRAM not disk directly. So the AFAIK the writes are always as sequential as they can be*

Reads are cached like crazy, esp when PAM/FlashCache etc.

*Generally when someone says they want to know they are looking for bottlenecks. I stand by statit as a tool for this since you are seeing how each disk is working. You might not know exactly what's causing the issue but it's good data to know what is going on at the aggregate level (which is what he is asking about) and the RG level (which is where the performance for an aggregate is going to be determined).

 Disk Statistics (per second)
    ut% is the percent of time the disk was busy.
    xfers is the number of data-transfer commands issued per second.
    xfers = ureads + writes + cpreads + greads + gwrites
    chain is the average number of 4K blocks per command.
    usecs is the average disk round-trip time per 4K block.



Jeremy Page | Senior Technical Architect | Gilbarco Veeder-Root, A Danaher Company
Office:336-547-5399 | Cell:336-601-7274 | 24x7 Emergency:336-430-8151
On 01/16/2014 04:56 PM, Jeff Mohler wrote:
Statit will get you the AMALGAMATED workload to disks on writes, not individual IOs.  There's nothing there.


On reads..sure, I can see that.  The un-cached client read IO requests+readahead..but still an amalgamated result aggregate wide since you have no data locality to be very precise about it.


On Thu, Jan 16, 2014 at 1:32 PM, Jeremy Page <jeremy.page@gilbarco.com> wrote:
statit will give it to you per disk

On 01/16/2014 04:25 PM, Martin wrote:
Hi,

I'm trying to characterize the workload on our Netapp Filer running VMware
over NFS and iSCSI for benchmarking purposes using IOmeter.  

Is it possible to determine what the percentage random sequential
distribution the workload is on a Filer e.g from a perfstat?

I've looked at vscsiStats but that is only per VM and not for the aggregate
workload on the Filer.



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