[CentOS] Filesystem writes unexpectedly slow (CentOS 6.4)

Tue Oct 14 02:38:39 UTC 2014
Joakim Ziegler <joakim at terminalmx.com>

On 13/10/14, 21:16, Peter wrote:
> On 10/14/2014 02:15 PM, Joakim Ziegler wrote:
>> I have a rather large box (2x8-core Xeon, 96GB RAM) where I have a
>> couple of disk arrays connected on an Areca controller. I just added a
>> new external array, 8 3TB drives in RAID5, and the testing I'm doing
>> right now is on this array, but this seems to be a problem on this
>> machine in general, on all file systems (even, possibly, NFS, but I'm
>> not sure about that one yet).

> The first thing I would check is that you have a BBU installed on the
> areca controller and that it is functioning properly (check the cli, I
> don't know the exact commands off the top of my head), also make sure
> that write caching is enabled on the controller (after you've checked
> the BBU, of course).  Without a working BBU in place hardware RAID
> controllers, such as areca, disable write caching (by default) and this
> will have a significant impact on write speeds.

> Note that newer controllers use a type of flash memory instead of a BBU.

Yes, I have a BBU and it's working. No write caching should, however, not affect 
raw device writes and filesystem writes so differently, I think.

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