Hi Tomas Thanks for the clarification. If I understood you right , you mean that 6 GB (including my 2.5GB files) has been written to the device and still occupy space on the device !!!
This is fair enough for this case since most of my files ended up in L2ARC .... Great ... But this brings two related questions 1. What are really in L2ARC ... is it my old workingset data files that have been updated but still in L2ARC ? or something else ? Metadata ? 2. More importantly, what if my workingset was larger that 2.5GB (Say 5GB), I guess my L2ARC device will be filled completely before all my workingset transfer to the L2ARC device !!! Thanks .... On Sat, Apr 3, 2010 at 4:31 PM, Tomas Ögren <st...@acc.umu.se> wrote: > On 02 April, 2010 - Abdullah Al-Dahlawi sent me these 128K bytes: > > > Hi all > > > > I ran a workload that reads & writes within 10 files each file is 256M, > ie, > > (10 * 256M = 2.5GB total Dataset Size). > > > > I have set the ARC max size to 1 GB on etc/system file > > > > In the worse case, let us assume that the whole dataset is hot, meaning > my > > workingset size= 2.5GB > > > > My SSD flash size = 8GB and being used for L2ARC > > > > No slog is used in the pool > > > > My File system record size = 8K , meaning 2.5% of 8GB is used for L2ARC > > Directory in ARC. which ultimately mean that available ARC is 1024M - > 204.8M > > = 819.2M Available ARC (Am I Right ?) > > Seems about right. > > > Now the Question ... > > > > After running the workload for 75 minutes, I have noticed that L2ARC > device > > has grown to 6 GB !!!!!!! ???? > > No, 6GB of the area has been touched by Copy on Write, not all of it is > in use anymore though. > > > What is in L2ARC beyond my 2.5GB Workingset ?? something else is has been > > added to L2ARC !!!! > > [ snip lots of data ] > > This is your last one: > > > module: zfs instance: 0 > > name: arcstats class: misc > > c 1073741824 > > c_max 1073741824 > > c_min 134217728 > [...] > > l2_size 2632226304 > > l2_write_bytes 6486009344 > > Roughly 6GB has been written to the device, and slightly less than 2.5GB > is actually in use. > > > p 775528448 > > /Tomas > -- > Tomas Ögren, st...@acc.umu.se, > http://www.acc.umu.se/~stric/<http://www.acc.umu.se/%7Estric/> > |- Student at Computing Science, University of Umeå > `- Sysadmin at {cs,acc}.umu.se > -- Abdullah Al-Dahlawi PhD Candidate George Washington University Department. Of Electrical & Computer Engineering ---- Check The Fastest 500 Super Computers Worldwide http://www.top500.org/list/2009/11/100
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