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Alerting about all zero content?

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Voyager

Alerting about all zero content?

I've been running performance tests with Microsoft DISKSPD on Nutanix. By default DISKSPD uses data sets which are "empty", filled with "Zero" characters. Nutanix will detect this and store data in special "Estore Zero" or "Oplog Zero" bucket, no data is written to disk. Only metadata gets updated with information "this block contains only zeros". When data is read, block content is generated in CPU/Memory, rather than reading anything from back-end storage.

 

Using DISKSPD or similar products writing only zeros will give overly positive performance figures and if used as base for performance sizing, can lead to grossly undersized environments.

 

Since data is already available in Stargate statistics, how about alerting about this?

 

"Hey there, it seems that you are running some sort of performance test. The tool you are using generates data with all-zero content. Using all-zero content will give overly positive performance figures. XX% of current workload for virtual machine X is all-zero content"

 

 

 

 

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Moderator Moderator
Moderator

Re: Alerting about all zero content?

i.e a "BS detector alert" Smiley Happy

 

The challenge here is that, its possible for an application to spit out all zero content, so getting stargate (or anything else) to pick up when you're actually just running a BS storage test, or when the application is actually doing something that slightly resembles a BS test (rare, but it could happen), could be tricky.

 

I love the zero suppression technology that we have, its actually quite a huge strength, and in my mind, no amount of fancy alerting is going to undo the fundamental misunderstanding that people having around running performance test (i.e, not everyone knows that DISKSPD generally is a bunch of zeros)

Jon Kohler | Principal Architect, Nutanix | Nutanix NPX #003, VCDX #116 | @JonKohler
Please Kudos if useful!
3 REPLIES
Moderator Moderator
Moderator

Re: Alerting about all zero content?

i.e a "BS detector alert" Smiley Happy

 

The challenge here is that, its possible for an application to spit out all zero content, so getting stargate (or anything else) to pick up when you're actually just running a BS storage test, or when the application is actually doing something that slightly resembles a BS test (rare, but it could happen), could be tricky.

 

I love the zero suppression technology that we have, its actually quite a huge strength, and in my mind, no amount of fancy alerting is going to undo the fundamental misunderstanding that people having around running performance test (i.e, not everyone knows that DISKSPD generally is a bunch of zeros)

Jon Kohler | Principal Architect, Nutanix | Nutanix NPX #003, VCDX #116 | @JonKohler
Please Kudos if useful!
Voyager

Re: Alerting about all zero content?

No worries, just an idea. Alerts giving false positives could lead to "crying wolf" Smiley Happy On the other hand, users could turn the alert off in case of too many false positives.

 

Problem with educating people about performance testing is that "You don't know, what you don't know". DiskSPD and it's predessor SQLIO are widely used as benchmarking tools, many times without too much understanding how they really work.

 

What is really scary with DISKSPD, is that it still generates zeros, even if instructed to use random data (-Z option). It seems that under the covers it uses poor random number generator. Depending on the alingnment of moon and sun, it will sometimes generate all zeros while the user might think that the data is random.

 

With Nutanix analytics it is very easy to catch these, if you know what to look for.

Moderator Moderator
Moderator

Re: Alerting about all zero content?

Gotcha, we're totally on the same page. Educating people on these "silly" tests is always an uphill battle.

 

For these situations, I often draw on the saying that "the amount of energy necessary to refute bullshit is an order of magnitude bigger than to produce it."

 

That said, we're working on illumintating these zero streams and highlighting Nutanix's strength in zero suppression in another way, thats an active effort in Engineering, should hit first half 2017 if we're lucky.

Jon Kohler | Principal Architect, Nutanix | Nutanix NPX #003, VCDX #116 | @JonKohler
Please Kudos if useful!