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https://issues.apache.org/jira/browse/LUCENE-5951?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14251642#comment-14251642
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Uwe Schindler commented on LUCENE-5951:
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I only found out that our detection *may* not work with LVM or MD devices,
unfortunately I cannot try it out:
http://lkml.iu.edu/hypermail/linux/kernel/1202.2/01578.html
Theoretically, the software RAID should pass this flag down unmodified, if
*all* devices are rotational or not. But it seems, it doesn't.
For the policeman machine, sda and sdb (both rotational) together create an md0
mirror RAID device, which reports rotational=1. This is good, but I am not sure
if this works if there are really SSDs as both raid devives (some people do
this using RAID0 devices to speed up sequential reads). Maybe somebody else can
report back, but I think the linux kernel puts rotational=1 for RAID devices as
a fixed value or this has changed in the meantime.
> Detect when index is on SSD and set dynamic defaults
> ----------------------------------------------------
>
> Key: LUCENE-5951
> URL: https://issues.apache.org/jira/browse/LUCENE-5951
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Michael McCandless
> Assignee: Michael McCandless
> Attachments: LUCENE-5951.patch, LUCENE-5951.patch, LUCENE-5951.patch,
> LUCENE-5951.patch, LUCENE-5951.patch, LUCENE-5951.patch
>
>
> E.g. ConcurrentMergeScheduler should default maxMergeThreads to 3 if it's on
> SSD and 1 if it's on spinning disks.
> I think the new NIO2 APIs can let us figure out which device we are mounted
> on, and from there maybe we can do os-specific stuff e.g. look at
> /sys/block/dev/queue/rotational to see if it's spinning storage or not ...
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