Thanks for very useful information.
Can you share more details about "Terrible bad performance" is compare against what? and what kind of usage pattern?
I'm just interested in key/value backend for more cost/performance without expensive HW such as ssd/fusion io.
Regards,
Satoru Funai
差出人: "Xiaoxi Chen" <xiaoxi.chen@xxxxxxxxx>
宛先: "Haomai Wang" <haomaiwang@xxxxxxxxx>
Cc: "Satoru Funai" <satoru.funai@xxxxxxxxx>, ceph-users@xxxxxxxx
送信済み: 2014年12月1日, 月曜日 午後 11:26:56
件名: RE: LevelDB support status is still experimental on Giant?
Range query is not that important in nowadays SSD----you can see very high read random read IOPS in ssd spec, and getting higher day by day.The key problem here is trying to exactly matching one query(get/put) to one SSD IO(read/write), eliminate the read/write amplification. We kind of believe OpenNvmKV may be the right approach.
Back to the context of Ceph, can we find some use case of nowadays key-value backend? We would like to learn from community what’s the workload pattern if you wants a K-V backed Ceph? Or just have a try? I think before we get a suitable DB backend ,we had better off to optimize the key-value backend code to support specified kind of load.
From: Haomai Wang [mailto:haomaiwang@xxxxxxxxx]
Sent: Monday, December 1, 2014 10:14 PM
To: Chen, Xiaoxi
Cc: Satoru Funai; ceph-users@xxxxxxxx
Subject: Re: LevelDB support status is still experimental on Giant?
Exactly, I'm just looking forward a better DB backend suitable for KeyValueStore. It maybe traditional B-tree design.
Kinetic original I think it was a good backend, but it doesn't support range query :-(
On Mon, Dec 1, 2014 at 10:04 PM, Chen, Xiaoxi <xiaoxi.chen@xxxxxxxxx> wrote:
We have tested it for a while, basically it seems kind of stable but show terrible bad performance.
This is not the fault of Ceph , but levelDB, or more generally, all K-V storage with LSM design(RocksDB,etc), the LSM tree structure naturally introduce very large write amplification---- 10X to 20X when you have tens GB of data per OSD. So you can always see very bad sequential write performance (~200MB/s for a 12SSD setup), we can share more details on the performance meeting.
To this end, key-value backend with LevelDB is not useable for RBD usage, but maybe workable(not tested) in the LOSF cases ( tons of small objects stored via rados , k-v backend can prevent the FS metadata become the bottleneck)
From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of Haomai Wang
Sent: Monday, December 1, 2014 9:48 PM
To: Satoru Funai
Cc: ceph-users@xxxxxxxx
Subject: Re: LevelDB support status is still experimental on Giant?
Yeah, mainly used by test env.
On Mon, Dec 1, 2014 at 6:29 PM, Satoru Funai <satoru.funai@xxxxxxxxx> wrote:
Hi guys,
I'm interested in to use key/value store as a backend of Ceph OSD.
When firefly release, LevelDB support is mentioned as experimental,
is it same status on Giant release?
Regards,
Satoru Funai
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Best Regards,
Wheat
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Best Regards,
Wheat
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