[jira] [Created] (IMPALA-5858) Impalad misleadingly reports RAM as a rotational disk

["Zoram Thanga (JIRA)" <ji...@apache.org>]

Zoram Thanga created IMPALA-5858:
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             Summary: Impalad misleadingly reports RAM as a rotational disk
                 Key: IMPALA-5858
                 URL: https://issues.apache.org/jira/browse/IMPALA-5858
             Project: IMPALA
          Issue Type: Bug
          Components: Backend
    Affects Versions: Impala 2.8.0
         Environment: Ubuntu 16.04, Dell Optiplex 7050
Linux xxxx-xxxx 4.4.0-36-generic #55-Ubuntu SMP Thu Aug 11 18:01:55 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

            Reporter: Zoram Thanga
            Priority: Minor


The informational startup log of impalad dumps a lot of information, including a report of all "disks" found on the system. The list of disks is obtained from /proc/partitions. For the entries in /proc/partitions, the code reads /sys/block/<device>/queue/rotational.

I0828 18:51:42.251794 31104 init.cc:218] Cpu Info:
  Model: Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz
  Cores: 8
  Max Possible Cores: 8
  L1 Cache: 32.00 KB (Line: 64.00 B)
  L2 Cache: 256.00 KB (Line: 64.00 B)
  L3 Cache: 8.00 MB (Line: 64.00 B)
  Hardware Supports:
    ssse3
    sse4_1
    sse4_2
    popcnt
    avx
    avx2
  Numa Nodes: 1
  Numa Nodes of Cores: 0->0 | 1->0 | 2->0 | 3->0 | 4->0 | 5->0 | 6->0 | 7->0 |
I0828 18:51:42.251799 31104 init.cc:219] Disk Info: 
  Num disks 3: 
*    ram (rotational=true)
    sda (rotational=true)
    sr (rotational=true)


For HDDs and SSDs this makes sense. But for RAM, it does not. It does not help that the kernel itself will flag /sys/block/ram{#}/queue/rotational as 1.

$ cat /sys/block/ram0/queue/rotational 
1
$

We probably should not report RAM as a disk, or special-case handling of RAM devices/partitions that show up in /proc/partitions.



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