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Re: [zfs-discuss] ZFS ARC cache issue

Subject: Re: [zfs-discuss] ZFS ARC cache issue
From: Richard Elling
Date: Thu, 3 Jun 2010 10:50:14 -0700
On Jun 3, 2010, at 10:33 AM, Ketan wrote:
> We are having a server running zfs root with 64G RAM and the system has 3 
> zones running oracle fusion app and zfs cache is using 40G memory as per 
> 
> kstat zfs:0:arcstats:size. and system shows only 5G of memory is free rest is 
> taken by kernel and 2 remaining zones. 
> 
> Now my problem is that fusion guys are getting not enough memory message 
> while starting their application due to top and vmstat shows 5G as free 
> memory. But i read ZFS cache releases memory as required by the application 
> so why fusion application is not starting up.

ZFS will release the memory, but sometimes this can take a moment
and in the meantime, applications which are not written to retry allocations
are likely to bail out.

> Is there some we can do to decrease the ARC Cache usage on the fly without 
> rebooting the global zone ?

This is a case where limiting the ARC size can be useful. For more information
see the ZFS Evil Tuning Guide
http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide#Limiting_the_ARC_Cache
 -- richard

-- 
Richard Elling
richard@xxxxxxxxxxx   +1-760-896-4422
ZFS and NexentaStor training, Rotterdam, July 13-15, 2010
http://nexenta-rotterdam.eventbrite.com/




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