How is storage different from chicken?
This is a story from the “Notes of a Service Engineer” series. We will answer the question a bit later, but first a small tale about one MASSIVE fall. Recently, a client addressed our Service Center and decided to upgrade the HDS AMS2000 array by itself: to replace part of the old disks with newer ones. According to the customer, he inserted a new disk - and one controller broke; pulled out a new disk - and the second controller also turned on the alarm indication, and access to the array was lost from all systems.
Ask the administrator questions about his actions. It turns out that it was this administrator who stepped in on his shift after they decided to pull out a new disk. As a result, the array was not included. According to the logs from the controllers, the controllers could not spin the discs, and there was no indication on the discs.
What could have happened here? We gathered a “consultation” of our service engineers, began to think. The first version: maybe when installing the disk, something happened to the disk backplane and it became inoperative? We decided to find an array chassis without controllers to replace the entire chassis along with backplane. Not finding it, they asked the customer to reload all the disks in the chassis with the controller and try to start an array.
And it was here that we were waited for by what is called “blow - and catharsis” (and that same “banana skin”, which dropped the entire system). It turned out that in the chassis with the controller the client pulled out the first five disks exactly (if you know what I mean)! It was their size that he wanted to increase. As long as attempts were made to reanimate the array, the disks were removed. Returned the old drives in place. And, lo and behold, the array is included!
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The moral of this fable is simple: only a chicken can run without a head, and even then not for long. The HDS Mid-Range on the first five disks stores a copy of the array configuration. When loading the array, it first tries to unwind the first 5 disks in the chassis with the controller. In case of failure (for example, due to the lack thereof), the download stops.
Nikolay Vedyashkin, expert of the Jet Infosystems Service Center.
Ask the administrator questions about his actions. It turns out that it was this administrator who stepped in on his shift after they decided to pull out a new disk. As a result, the array was not included. According to the logs from the controllers, the controllers could not spin the discs, and there was no indication on the discs.
What could have happened here? We gathered a “consultation” of our service engineers, began to think. The first version: maybe when installing the disk, something happened to the disk backplane and it became inoperative? We decided to find an array chassis without controllers to replace the entire chassis along with backplane. Not finding it, they asked the customer to reload all the disks in the chassis with the controller and try to start an array.
And it was here that we were waited for by what is called “blow - and catharsis” (and that same “banana skin”, which dropped the entire system). It turned out that in the chassis with the controller the client pulled out the first five disks exactly (if you know what I mean)! It was their size that he wanted to increase. As long as attempts were made to reanimate the array, the disks were removed. Returned the old drives in place. And, lo and behold, the array is included!
')
The moral of this fable is simple: only a chicken can run without a head, and even then not for long. The HDS Mid-Range on the first five disks stores a copy of the array configuration. When loading the array, it first tries to unwind the first 5 disks in the chassis with the controller. In case of failure (for example, due to the lack thereof), the download stops.
Nikolay Vedyashkin, expert of the Jet Infosystems Service Center.
Source: https://habr.com/ru/post/320636/
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