I also noticed that, Cassandra appears to perform better under a continues load.
Are you sure the rows you're quering are actually in the cache? 2012/2/13 Franc Carter <franc.car...@sirca.org.au> > 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 > >
