Re: [RFC PATCH] ceph: Write through cache support based on fscache

2013-11-02 Thread Li Wang
Hi Milosz, Thanks for your comments. We think SSD and fscache based write cache is definitely useful for Ceph, since to some extent, write amplification slow down the write performance of Ceph. Lustre has already introduced SSD based write cache. SSD can be treated as an outer big cache

Re: [RFC PATCH] ceph: Write through cache support based on fscache

2013-11-02 Thread Li Wang
Hi Milosz, Thanks for your comments. We think SSD and fscache based write cache is definitely useful for Ceph, since to some extent, write amplification slow down the write performance of Ceph. Lustre has already introduced SSD based write cache. SSD can be treated as an outer big cache

Re: [RFC PATCH] ceph: Write through cache support based on fscache

2013-11-01 Thread Milosz Tanski
Li, I think it would be fantastic to see a write cache. In many workloads you ended up writing out a file and then turning around and reading it right back in on the same node. There's a few things that I would like to see. First, an mount option to turn on/off write through caching. There are

[RFC PATCH] ceph: Write through cache support based on fscache

2013-11-01 Thread Li Wang
Currently, fscache only plays as read cache for ceph, this patch enables it plays as the write through cache as well. A small trick to be discussed: if the writing to OSD finishes before the writing to fscache, the fscache writing is cancelled to avoid slow down the writepages() process.

[RFC PATCH] ceph: Write through cache support based on fscache

2013-11-01 Thread Li Wang
Currently, fscache only plays as read cache for ceph, this patch enables it plays as the write through cache as well. A small trick to be discussed: if the writing to OSD finishes before the writing to fscache, the fscache writing is cancelled to avoid slow down the writepages() process.

Re: [RFC PATCH] ceph: Write through cache support based on fscache

2013-11-01 Thread Milosz Tanski
Li, I think it would be fantastic to see a write cache. In many workloads you ended up writing out a file and then turning around and reading it right back in on the same node. There's a few things that I would like to see. First, an mount option to turn on/off write through caching. There are