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From Tommy Lee <glico...@gmail.com>
Subject Re: Randomly high read rates
Date Wed, 18 Mar 2015 16:41:23 GMT
Allan,

   This can be my problem. I see some fallbacks in debug log.
   Do you know if there is some development in progress or workaround for
this case ?
   Thanks,



2015-03-17 18:38 GMT-03:00 Alan Carroll <solidwallofcode@yahoo-inc.com>:

> One thing to check for is (1) large objects in the cache and (2)
> multi-range requests. In this case ATS will read the entire object and
> filter out that parts that aren't in the range requests. The standard range
> acceleration only works for single range requests. Every object resides on
> a single disk so if this is a specific object you would see this heavy read
> only on that disk. There is a debug message for this but unfortunately it's
> "http_trans" which generates *a lot* of output. If you're willing to do a
> minor tweak of the source, look in HttpSM.cc for the line reading "Unable
> to accelerate range request" and change the tag from "http_trans" to
> something more specific such as "http_trans_range" and then use that as the
> debug tag.
>
> This may not be the problem, but it is worth taking a look.
>
>
>
>   On Tuesday, March 17, 2015 4:12 PM, Tommy Lee <glicosao@gmail.com>
> wrote:
>
>
> Hi everybody,
>
>    We are using ATS 4.2.1 with raw disks config and volume and hosting
> configs enabled.
>    And we're experiencing strange high read rates randomly at one disk.
>    We use LSI Megaraid configured with RAID 0 ( Write back, Read Ahead,
> Cached IO and write cache, strip size 1MB ).
>    My question is: There is someway to see with debug tags what's is going
> on ?
>
>    ATS can be performing some maintenance tasks that randomly read disk at
> higher rates ?
>
>    IOPs goes up to 450 and read speed reaches (90 MB/s) staying for 30~50
> seconds and then goes back to normal.
>
> I would thank if anyone can give some direction where to search for this
> debug inside the code.
>
>
> Best regards,
>
>
>
>

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