… volume per second. Now keep in account Innodb double write buffer (so writes to Innodb tablespace are double) and the fact you…. Of course depending on database or workload this may need to be adjusted. If you have 10GB database size (including logs etc) you will not need 18GB undo snapshot no matter how heavy IO is. Also…
Post: Tokyo Tyrant - The Extras Part I : Is it Durable?
November 10, 2009 By 5 Comments
… what’s going on: /* Synchronize updated contents of a hash database object with the file and the device. */ bool tchdbsync(TCHDB… is tchdbmemsync. /* Synchronize updating contents on memory of a hash database object. */ bool tchdbmemsync(TCHDB *hdb, bool phys){ assert(hdb); if… while I did not see a drop in my benchmark, heavy write operations will see a drop in performance… for instance with…
Post: dbqp and Xtrabackup testing
November 16, 2011 By Leave a Comment
… be desired. The randgen is a literal wonder-tool for database testing, but it is also occasionally frustrating / doesn’t scratch… fancy, basically, we take advantage of Python’s unittest and write classes that use their code. The biggest bit dbqp does… tests by creating heavy randgen loads against the master during backup and slave setup, and other assorted crimes against database software. We…
Post: Aligning IO on a hard disk RAID – the Benchmarks
June 9, 2011 By 13 Comments
… which is usually light on writes (especially if there’s a BBU protected Write-Back cache) and heavy on random reads. Regardless of… customer was running a database which was way bigger than 16G, I’ve repeated the random read (and write) benchmark with 8… the two workloads that are most relevant to databases – random reads and random writes – IO alignment on a 4-disk RAID10 with…
Comment: Disaster: MySQL 5.5 Flushing
September 19, 2011 By 27 Comments
…. Let’s compare: NDB has database in memory. InnoDB has buffer pool in memory. NDB writes REDO log. InnoDB does too. NDB has a background thread that periodically dumps contents of full in-memory database to…, if I have a 100G or 200G buffer pool and heavy write workload, would it be advantageous to just periodically dump the…
Comment: Tokyo Tyrant - The Extras Part I : Is it Durable?
August 20, 2010 By 5 Comments
… tunable fillfactor) the table itself can be tuned so that write hotspots – in conjunction with any striped RAID – are more likely… have to tune the OS more in keeping with a database machine. Think: AS/400 or S390. One can can even… times of the day/month/year for the a write-intensive periods of heavy writes to flush its dirty pages quickly & regularly in…
Post: InnoDB Flushing: a lot of memory and slow disk
March 31, 2011 By 57 Comments
… nowadays, for example Cisco UCS C250), your database fits into memory, and your write rate is significant, then the slow disk is… flushing neighbor pages was implemented to perform sequential writes where possible and avoid random writes, which is quite critical for hard drives… systems, or is affected by periodic tasks like backup or heavy background queries.) If we see that flushing to disk is…
Comment: Why you don't want to shard.
August 6, 2009 By 34 Comments
… that are on separate machines one ends up writing the join in the application server, which is …sql statement. Effectively, one is no longer using the database to full potential and it isn’t that … flexibility, but as pointed out, with a heavy, often too heavy, operational cost. I’m not saying that …
Post: Is disk Everything for MySQL Performance ?
April 25, 2008 By 7 Comments
… backups etc – because Sphinx is doing all search heavy lifting we only need to insert new data… on the raid volume impact on transactional log write speed is usually minimal. At the same time… why. A lot of pieces – filesystem, disk scheduling, database buffer management can be rather complex but you…
Post: InnoDB's gap locks
March 27, 2012 By 15 Comments
… the row level locking. This feature provides better concurrency under heavy write load but needs additional precautions to avoid phantom reads and… consistent Statement based replication. To accomplish that, row level locking databases also acquire gap locks. What is a Phantom Read A…
