[Openstack] [swift] Issue of cache eating up most of memory

John Dickinson me at not.mn
Tue Aug 27 14:28:36 UTC 2013

This seems to be a popular question this morning... Take a look at http://lists.openstack.org/pipermail/openstack/2013-August/000849.html and https://answers.launchpad.net/swift/+question/234691 as well.

The page cache usage means that the system has to go to disk to get the data when it is requested. This is slow, especially when eg a single container  is being used frequently. The slowness of spinning drives, especially when they are busy with lots of requests, can lead to timeouts in the system. Beyond the pithy "buy more memory" answer, there are a couple of things you can do. First, you can deploy account and container servers on high-IOPS devices (eg SSDs). Second, you can deploy account and container servers on separate physical machines than the object servers. Larger clusters (either measured by capacity or by throughput needs) generally end up employing both of these strategies to ensure a highly performant Swift cluster.


On Aug 27, 2013, at 7:15 AM, Hua ZZ Zhang <zhuadl at cn.ibm.com> wrote:

> Hi Stackers,
> We have memory issue when running COSbench tool against Swift. The memory was consumed rapidly by Swift.
> I carefully checked the memory info and found most of the memory was consumed by page cache and inode cache. It will
> fail the server to accept any request.  I know it can be released by using the command of echo 3 > /proc/sys/drop_caches. 
> But does anybody have better solution to address this issue? 
> -Zhang Hua (Edward)
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