Re: Are Cassandra writes are faster than reads?

They can be and it depends on your compaction strategy :) On Sun, 6 Nov 2016 at 21:24 Ali Akhtar wrote: > tl;dr? I just want to know if updates are bad for performance, and if so, > for how long. > > On Mon, Nov 7, 2016 at 10:23 AM, Ben Bromhead

Re: Is it a memory issue?

Yes, it does mean you’re getting ahead of Cassandra’s ability to keep up although I would have probably expected a higher number of pending compactions before you got serious issues (I’ve seen numbers in the thousands). I notice from the screenshot you provide that you are using secondary

Re: Is it a memory issue?

Thanks Ben. I stopped inserting and checked compaction status as you mentioned. Seems there is lots of compaction work waiting to do. Please see below. In this case is it a sign that writting faster than C* can process? One node, [root@iZbp11zpafrqfsiys90kzoZ bin]# ./nodetool compactionstats

Re: Are Cassandra writes are faster than reads?

tl;dr? I just want to know if updates are bad for performance, and if so, for how long. On Mon, Nov 7, 2016 at 10:23 AM, Ben Bromhead wrote: > Check out https://wiki.apache.org/cassandra/WritePathForUsers for the > full gory details. > > On Sun, 6 Nov 2016 at 21:09 Ali

Re: Are Cassandra writes are faster than reads?

Check out https://wiki.apache.org/cassandra/WritePathForUsers for the full gory details. On Sun, 6 Nov 2016 at 21:09 Ali Akhtar wrote: > How long does it take for updates to get merged / compacted into the main > data file? > > On Mon, Nov 7, 2016 at 5:31 AM, Ben Bromhead

Re: Are Cassandra writes are faster than reads?

How long does it take for updates to get merged / compacted into the main data file? On Mon, Nov 7, 2016 at 5:31 AM, Ben Bromhead wrote: > To add some flavor as to how the commitlog implementation is so quick. > > It only flushes to disk every 10s by default. So writes are

Re: Is it a memory issue?

This sounds to me like your writes go ahead of compactions trying to keep up which can eventually cause issues. Keep an eye on nodetool compactionstats if the number of compactions continually climbs then you are writing faster than Cassandra can actually process. If this is happening then you

Is it a memory issue?

Hi All, We have one issue on C* testing. At first the inserting was very fast and TPS was about 30K/s, but when the size of data rows reached 2 billion, the insertion rate decreased very badly and the TPS was 20K/s. When the size of rows reached 2.3 billion, the TPS decreased to 0.5K/s, and

Re: Are Cassandra writes are faster than reads?

To add some flavor as to how the commitlog implementation is so quick. It only flushes to disk every 10s by default. So writes are effectively done to memory and then to disk asynchronously later on. This is generally accepted to be OK, as the write is also going to other nodes. You can of

Designing a table in cassandra

Hi, We are new to Cassandra. For our POC, we tried creating table and inserting them as JSON and all these went fine. Now we are trying to implement one of the application scenario, and I am having difficulty in coming up with the best approach. Scenario: We have a Device POJO which have some

Re: Are Cassandra writes are faster than reads?

Cassandra writes are particularly fast, for a few reasons: 1) Most writes go to a commitlog (append-only file, written linearly, so particularly fast in terms of disk operations) and then pushed to the memTable. Memtable is flushed in batches to the permanent data files, so it buffers

Are Cassandra writes are faster than reads?

Hi all, Are Cassandra writes are faster than reads ?? If yes, why is this so? I am using consistency 1 and data is in memory. Vikas