2012/2/13 R. Verlangen <ro...@us2.nl> > This is because of the "warm up" of Cassandra as it starts. On a start it > will start fetching the rows that were cached: this will have to be loaded > from the disk, as there is nothing in the cache yet. You can read more > about this at http://wiki.apache.org/cassandra/LargeDataSetConsiderations >
I actually has the opposite 'problem'. I have a pair of servers that have been static since mid last week, but have seen performance vary significantly (x10) for exactly the same query. I hypothesised it was various caches so I shut down Cassandra, flushed the O/S buffer cache and then bought it back up. The performance wasn't significantly different to the pre-flush performance cheers > > > 2012/2/13 Franc Carter <franc.car...@sirca.org.au> > >> On Mon, Feb 13, 2012 at 5:03 PM, zhangcheng <zhangch...@jike.com> wrote: >> >>> ** >>> >>> I think the keycaches and rowcahches are bothe persisted to disk when >>> shutdown, and restored from disk when restart, then improve the performance. >>> >> >> Thanks - that would explain at least some of what I am seeing >> >> cheers >> >> >>> >>> 2012-02-13 >>> ------------------------------ >>> zhangcheng >>> ------------------------------ >>> *发件人：* Franc Carter >>> *发送时间：* 2012-02-13 13:53:56 >>> *收件人：* user >>> *抄送：* >>> *主题：* keycache persisted to disk ? >>> >>> Hi, >>> >>> I am testing Cassandra on Amazon and finding performance can vary fairly >>> wildly. I'm leaning towards it being an artifact of the AWS I/O system but >>> have one other possibility. >>> >>> Are keycaches persisted to disk and restored on a clean shutdown and >>> restart ? >>> >>> cheers >>> >>> -- >>> >>> *Franc Carter* | Systems architect | Sirca Ltd >>> <marc.zianideferra...@sirca.org.au> >>> >>> franc.car...@sirca.org.au | www.sirca.org.au >>> >>> Tel: +61 2 9236 9118 >>> >>> Level 9, 80 Clarence St, Sydney NSW 2000 >>> >>> PO Box H58, Australia Square, Sydney NSW 1215 >>> >>> >> >> >> -- >> >> *Franc Carter* | Systems architect | Sirca Ltd >> <marc.zianideferra...@sirca.org.au> >> >> franc.car...@sirca.org.au | www.sirca.org.au >> >> Tel: +61 2 9236 9118 >> >> Level 9, 80 Clarence St, Sydney NSW 2000 >> >> PO Box H58, Australia Square, Sydney NSW 1215 >> >> > -- *Franc Carter* | Systems architect | Sirca Ltd <marc.zianideferra...@sirca.org.au> franc.car...@sirca.org.au | www.sirca.org.au Tel: +61 2 9236 9118 Level 9, 80 Clarence St, Sydney NSW 2000 PO Box H58, Australia Square, Sydney NSW 1215
