2012/2/13 R. Verlangen <ro...@us2.nl> > 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? >
I'm making an assumption . . . I don't yet know enough about cassandra to prove they are in the cache. I have my keycache set to 2 million, and am only querying ~900,000 keys. so after the first time I'm assuming they are in the cache. cheers > > > 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 >> >> > -- *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
