cassandra-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Apache Wiki <>
Subject [Cassandra Wiki] Update of "FAQ_JP" by shot6
Date Sun, 11 Apr 2010 02:01:43 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Cassandra Wiki" for change notification.

The "FAQ_JP" page has been changed by shot6.


- == I delete data from Cassandra, but disk usage stays the same. What gives? ==
- Data you write to Cassandra gets persisted to SSTables. Since SSTables are immutable, the
data can't actually be removed when you perform a delete, instead, a marker (also called a
"tombstone") is written to indicate the value's new status. Never fear though, on the first
compaction that occurs after ''GCGraceSeconds'' (hint: storage-conf.xml) have expired, the
data will be expunged completely and the corresponding disk space recovered. See DistributedDeletes
for more detail.
+ == Cassandraからデータを削除したのにディスク使用量は同じです.何が起こってるのでしょうか?
+ Cassandraに書き込まれたデータは[[MemtableSSTable_JP|SSTables]]に書き込まれます.SSTablesはイミュータブルで、データ削除を実行してもマーカー(tombstoneといいます)が書き込まれるだけで実際には削除されません.でも大丈夫.GCGraceSeconds後の最初のコンパクションでデータは完璧に抹消され、ディスクスペースはそのときに軽減されます.詳しくは[[DistributedDeletes_JP|DistributedDeletes]]を参照してください.
  == Why are reads slower than writes? ==

View raw message