For a row cache of 1,650,000: 16 byte token 300 byte row key ? and row data ? multiply by a java fudge factor or 5 or 10.
Trying delete the saved cache and restarting. Cheers ----------------- Aaron Morton Freelance Cassandra Developer New Zealand @aaronmorton http://www.thelastpickle.com On 15/11/2012, at 8:20 PM, Wz1975 <wz1...@yahoo.com> wrote: > Before shut down, you saw rowcache has 500m, 1.6m rows, each row average > 300B, so 700k row should be a little over 200m, unless it is reading more, > maybe tombstone? Or the rows on disk have grown for some reason, but row > cache was not updated? Could be something else eats up the memory. You may > profile memory and see who consumes the memory. > > > Thanks. > -Wei > > Sent from my Samsung smartphone on AT&T > > > -------- Original message -------- > Subject: Re: unable to read saved rowcache from disk > From: Manu Zhang <owenzhang1...@gmail.com> > To: user@cassandra.apache.org > CC: > > > 3G, other jvm parameters are unchanged. > > > On Thu, Nov 15, 2012 at 2:40 PM, Wz1975 <wz1...@yahoo.com> wrote: > How big is your heap? Did you change the jvm parameter? > > > > Thanks. > -Wei > > Sent from my Samsung smartphone on AT&T > > > -------- Original message -------- > Subject: Re: unable to read saved rowcache from disk > From: Manu Zhang <owenzhang1...@gmail.com> > To: user@cassandra.apache.org > CC: > > > add a counter and print out myself > > > On Thu, Nov 15, 2012 at 1:51 PM, Wz1975 <wz1...@yahoo.com> wrote: > Curious where did you see this? > > > Thanks. > -Wei > > Sent from my Samsung smartphone on AT&T > > > -------- Original message -------- > Subject: Re: unable to read saved rowcache from disk > From: Manu Zhang <owenzhang1...@gmail.com> > To: user@cassandra.apache.org > CC: > > > OOM at deserializing 747321th row > > > On Thu, Nov 15, 2012 at 9:08 AM, Manu Zhang <owenzhang1...@gmail.com> wrote: > oh, as for the number of rows, it's 1650000. How long would you expect it to > be read back? > > > On Thu, Nov 15, 2012 at 3:57 AM, Wei Zhu <wz1...@yahoo.com> wrote: > Good information Edward. > For my case, we have good size of RAM (76G) and the heap is 8G. So I set the > row cache to be 800M as recommended. Our column is kind of big, so the hit > ratio for row cache is around 20%, so according to datastax, might just turn > the row cache altogether. > Anyway, for restart, it took about 2 minutes to load the row cache > > INFO [main] 2012-11-14 11:43:29,810 AutoSavingCache.java (line 108) reading > saved cache /var/lib/cassandra/saved_caches/XXX-f2-RowCache > INFO [main] 2012-11-14 11:45:12,612 ColumnFamilyStore.java (line 451) > completed loading (102801 ms; 21125 keys) row cache for XXX.f2 > > Just for comparison, our key is long, the disk usage for row cache is 253K. > (it only stores key when row cache is saved to disk, so 253KB/ 8bytes = 31625 > number of keys). It's about right... > So for 15MB, there could be a lot of "narrow" rows. (if the key is Long, > could be more than 1M rows) > > Thanks. > -Wei > From: Edward Capriolo <edlinuxg...@gmail.com> > To: user@cassandra.apache.org > Sent: Tuesday, November 13, 2012 11:13 PM > Subject: Re: unable to read saved rowcache from disk > > http://wiki.apache.org/cassandra/LargeDataSetConsiderations > > A negative side-effect of a large row-cache is start-up time. The > periodic saving of the row cache information only saves the keys that > are cached; the data has to be pre-fetched on start-up. On a large > data set, this is probably going to be seek-bound and the time it > takes to warm up the row cache will be linear with respect to the row > cache size (assuming sufficiently large amounts of data that the seek > bound I/O is not subject to optimization by disks) > > Assuming a row cache 15MB and the average row is 300 bytes, that could > be 50,000 entries. 4 hours seems like a long time to read back 50K > entries. Unless the source table was very large and you can only do a > small number / reads/sec. > > On Tue, Nov 13, 2012 at 9:47 PM, Manu Zhang <owenzhang1...@gmail.com> wrote: > > "incorrect"... what do you mean? I think it's only 15MB, which is not big. > > > > > > On Wed, Nov 14, 2012 at 10:38 AM, Edward Capriolo <edlinuxg...@gmail.com> > > wrote: > >> > >> Yes the row cache "could be" incorrect so on startup cassandra verify they > >> saved row cache by re reading. It takes a long time so do not save a big > >> row > >> cache. > >> > >> > >> On Tuesday, November 13, 2012, Manu Zhang <owenzhang1...@gmail.com> wrote: > >> > I have a rowcache provieded by SerializingCacheProvider. > >> > The data that has been read into it is about 500MB, as claimed by > >> > jconsole. After saving cache, it is around 15MB on disk. Hence, I suppose > >> > the size from jconsole is before serializing. > >> > Now while restarting Cassandra, it's unable to read saved rowcache back. > >> > By "unable", I mean around 4 hours and I have to abort it and remove > >> > cache > >> > so as not to suspend other tasks. > >> > Since the data aren't huge, why Cassandra can't read it back? > >> > My Cassandra is 1.2.0-beta2. > > > > > > > > > > 9
