Wow. First, thanks a lot all for jumping into this. Let me try to reply to everyone in a single post.
> How many Gets you batch together in one call I tried with multiple different values from 10 to 3000 with similar results. Time to read 10 lines : 181.0 mseconds (55 lines/seconds) Time to read 100 lines : 484.0 mseconds (207 lines/seconds) Time to read 1000 lines : 4739.0 mseconds (211 lines/seconds) Time to read 3000 lines : 13582.0 mseconds (221 lines/seconds) > Is this equal to the Scan#setCaching () that u are using? The scan call is done after the get test. So I can't set the cache for the scan before I do the gets. Also, I tried to run them separatly (On time only the put, one time only the get, etc.) so I did not find a way to setup the cache for the get. > If both are same u can be sure that the the number of NW calls is coming > almost same. Here are the results for 10 000 gets and 10 000 scan.next(). Each time I access the result to be sure they are sent to the client. (gets) Time to read 10000 lines : 36620.0 mseconds (273 lines/seconds) (scan) Time to read 10000 lines : 119.0 mseconds (84034 lines/seconds) >[Block caching is enabled?] Good question. I don't know :( Is it enabled by default? How can I verify or activate it? > Also have you tried using Bloom filters? Not yet. They are on page 381 on Lars' book and I'm only on page 168 ;) > What's the hbase version you're using? I manually installed 0.94.0. I can try with an other version. > Is it repeatable? Yes. I tries many many times by adding some options, closing some process on the server side, remonving one datanode, adding one, etc. I can see some small variations, but still in the same range. I was able to move from 200 rows/second to 300 rows/second. But that's not really a significant improvment. Also, here are the results for 7 iterations of the same code. Time to read 1000 lines : 4171.0 mseconds (240 lines/seconds) Time to read 1000 lines : 3439.0 mseconds (291 lines/seconds) Time to read 1000 lines : 3953.0 mseconds (253 lines/seconds) Time to read 1000 lines : 3801.0 mseconds (263 lines/seconds) Time to read 1000 lines : 3680.0 mseconds (272 lines/seconds) Time to read 1000 lines : 3493.0 mseconds (286 lines/seconds) Time to read 1000 lines : 4549.0 mseconds (220 lines/seconds) >If the locations are wrong (region moved) you will have a retry loop I have one dead region. It's a server I brought down few days ago because it was to slow. But it's still on the hbase web interface. However, if I look at the table, there is no table region hosted on this server. Hadoop also was removed from it so it's saying one dead node. >Do you have anything in the logs? Nothing special. Only some "Block cache LRU eviction" entries. > Could you share as well the code Eveything is at the end of this post. >You can also check the cache hit and cache miss statistics that appears on the UI? Can you please tell me how I can find that? I was not able to find that on the web UI. Where should I look? > In your random scan how many Regions are scanned I only have 5 regions servers and 12 table regions. So I guess all the servers are called. So here is the code for the gets. I removed the KeyOnlyFilter because it's not improving the results. JM http://pastebin.com/K75nFiQk (for syntax highligthing) HTable table = new HTable(config, "test3"); for (int iteration = 0; iteration < 10; iteration++) { final int linesToRead = 1000; System.out.println(new java.util.Date () + " Processing iteration " + iteration + "... "); Vector<Get> gets = new Vector<Get>(linesToRead); for (long l = 0; l < linesToRead; l++) { byte[] array1 = new byte[24]; for (int i = 0; i < array1.length; i++) array1[i] = (byte)Math.floor(Math.random() * 256); Get g = new Get (array1); gets.addElement(g); processed++; } Object[] results = new Object[gets.size()]; long timeBefore = System.currentTimeMillis(); table.batch(gets, results); long timeAfter = System.currentTimeMillis(); float duration = timeAfter - timeBefore; System.out.println ("Time to read " + gets.size() + " lines : " + duration + " mseconds (" + Math.round(((float)linesToRead / (duration / 1000))) + " lines/seconds)"); for (int i = 0; i < results.length; i++) { if (results[i] instanceof KeyValue) if (!((KeyValue)results[i]).isEmptyColumn()) System.out.println("Result[" + i + "]: " + results[i]); // co BatchExample-9-Dump Print all results. } 2012/6/28, Ramkrishna.S.Vasudevan <ramkrishna.vasude...@huawei.com>: > Hi > > You can also check the cache hit and cache miss statistics that appears on > the UI? > > In your random scan how many Regions are scanned whereas in gets may be > many > due to randomness. > > Regards > Ram > >> -----Original Message----- >> From: N Keywal [mailto:nkey...@gmail.com] >> Sent: Thursday, June 28, 2012 2:00 PM >> To: user@hbase.apache.org >> Subject: Re: Scan vs Put vs Get >> >> Hi Jean-Marc, >> >> Interesting.... :-) >> >> Added to Anoop questions: >> >> What's the hbase version you're using? >> >> Is it repeatable, I mean if you try twice the same "gets" with the >> same client do you have the same results? I'm asking because the >> client caches the locations. >> >> If the locations are wrong (region moved) you will have a retry loop, >> and it includes a sleep. Do you have anything in the logs? >> >> Could you share as well the code you're using to get the ~100 ms time? >> >> Cheers, >> >> N. >> >> On Thu, Jun 28, 2012 at 6:56 AM, Anoop Sam John <anoo...@huawei.com> >> wrote: >> > Hi >> > How many Gets you batch together in one call? Is this equal to >> the Scan#setCaching () that u are using? >> > If both are same u can be sure that the the number of NW calls is >> coming almost same. >> > >> > Also you are giving random keys in the Gets. The scan will be always >> sequential. Seems in your get scenario it is very very random reads >> resulting in too many reads of HFile block from HDFS. [Block caching is >> enabled?] >> > >> > Also have you tried using Bloom filters? ROW blooms might improve >> your get performance. >> > >> > -Anoop- >> > ________________________________________ >> > From: Jean-Marc Spaggiari [jean-m...@spaggiari.org] >> > Sent: Thursday, June 28, 2012 5:04 AM >> > To: user >> > Subject: Scan vs Put vs Get >> > >> > Hi, >> > >> > I have a small piece of code, for testing, which is putting 1B lines >> > in an existing table, getting 3000 lines and scanning 10000. >> > >> > The table is one family, one column. >> > >> > Everything is done randomly. Put with Random key (24 bytes), fixed >> > family and fixed column names with random content (24 bytes). >> > >> > Get (batch) is done with random keys and scan with RandomRowFilter. >> > >> > And here are the results. >> > Time to insert 1000000 lines: 43 seconds (23255 lines/seconds) >> > That's correct for my needs based on the poor performances of the >> > servers in the cluster. I'm fine with the results. >> > >> > Time to read 3000 lines: 11444.0 mseconds (262 lines/seconds) >> > This is way to low. I don't understand why. So I tried the random >> scan >> > because I'm not able to figure the issue. >> > >> > Time to read 10000 lines: 108.0 mseconds (92593 lines/seconds) >> > This it impressive! I have added that after I failed with the get. I >> > moved from 262 lines per seconds to almost 100K lines/seconds!!! It's >> > awesome! >> > >> > However, I'm still wondering what's wrong with my gets. >> > >> > The code is very simple. I'm using Get objects that I'm executing in >> a >> > Batch. I tried to add a filter but it's not helping. Here is an >> > extract of the code. >> > >> > for (long l = 0; l < linesToRead; l++) >> > { >> > byte[] array1 = new byte[24]; >> > for (int i = 0; i < array1.length; >> i++) >> > array1[i] = >> (byte)Math.floor(Math.random() * 256); >> > Get g = new Get (array1); >> > gets.addElement(g); >> > } >> > Object[] results = new >> Object[gets.size()]; >> > System.out.println(new java.util.Date >> () + " \"gets\" created."); >> > long timeBefore = >> System.currentTimeMillis(); >> > table.batch(gets, results); >> > long timeAfter = System.currentTimeMillis(); >> > >> > float duration = timeAfter - timeBefore; >> > System.out.println ("Time to read " + >> gets.size() + " lines : " >> > + duration + " mseconds (" + Math.round(((float)linesToRead / >> > (duration / 1000))) + " lines/seconds)"); >> > >> > What's wrong with it? I can't add the setBatch neither I can add >> > setCaching because it's not a scan. I tried with different numbers of >> > gets but it's almost always the same speed. Am I using it the wrong >> > way? Does anyone have any advice to improve that? >> > >> > Thanks, >> > >> > JM > >
