Re: cassandra disks cache on SSD

2016-04-03 Thread Mateusz Korniak 
On Friday 01 April 2016 21:48:08 vincent gromakowski wrote:
> 2016-04-01 19:27 GMT+02:00 Mateusz Korniak :
> > We are using lvmcache for that.
>
> Can you provide me a approximate estimation of performance gain ?
 
I suspect it depends on frequently read data size. If it fits into caching 
SSDs.
In our scenario, adding one 250GB SSD to nodes owning 1.2 TB resulted in 75% 
read cache hit ratio.
It was enough to stop nodes being I/O bound and application to work without 
read timeouts.  

-- 
Mateusz Korniak
"(...) mam brata - poważny, domator, liczykrupa, hipokryta, pobożniś,
krótko mówiąc - podpora społeczeństwa."
Nikos Kazantzakis - "Grek Zorba"

Re: cassandra disks cache on SSD

2016-04-02 Thread Bryan Cheng 
Hi Vincent, have you already tried the more common tuning operations like
row cache?

I haven't done any disk level caching like this (we use SSD's exclusively),
but you may see some benefit from putting your commitlog on a separate
conventional HDD if you haven't tried this already. This may push your
read/write pattern to do more sequential access.

On Fri, Apr 1, 2016 at 12:48 PM, vincent gromakowski <
vincent.gromakow...@gmail.com> wrote:

> Can you provide me a approximate estimation of performance gain ?
>
> 2016-04-01 19:27 GMT+02:00 Mateusz Korniak :
>
>> On Friday 01 April 2016 13:16:53 vincent gromakowski wrote:
>> > (...)  looking
>> > for a way to use some kind of tiering with few SSD caching hot data from
>> > HDD.
>> > I have identified two solutions (...)
>>
>> We are using lvmcache for that.
>> Regards,
>> --
>> Mateusz Korniak
>> "(...) mam brata - poważny, domator, liczykrupa, hipokryta, pobożniś,
>> krótko mówiąc - podpora społeczeństwa."
>> Nikos Kazantzakis - "Grek Zorba"
>>
>>
>

Re: cassandra disks cache on SSD

2016-04-01 Thread vincent gromakowski 
Can you provide me a approximate estimation of performance gain ?

2016-04-01 19:27 GMT+02:00 Mateusz Korniak :

> On Friday 01 April 2016 13:16:53 vincent gromakowski wrote:
> > (...)  looking
> > for a way to use some kind of tiering with few SSD caching hot data from
> > HDD.
> > I have identified two solutions (...)
>
> We are using lvmcache for that.
> Regards,
> --
> Mateusz Korniak
> "(...) mam brata - poważny, domator, liczykrupa, hipokryta, pobożniś,
> krótko mówiąc - podpora społeczeństwa."
> Nikos Kazantzakis - "Grek Zorba"
>
>

Re: cassandra disks cache on SSD

2016-04-01 Thread Mateusz Korniak 
On Friday 01 April 2016 13:16:53 vincent gromakowski wrote:
> (...)  looking
> for a way to use some kind of tiering with few SSD caching hot data from
> HDD.
> I have identified two solutions (...)

We are using lvmcache for that.
Regards,
-- 
Mateusz Korniak
"(...) mam brata - poważny, domator, liczykrupa, hipokryta, pobożniś,
krótko mówiąc - podpora społeczeństwa."
Nikos Kazantzakis - "Grek Zorba"

cassandra disks cache on SSD

2016-04-01 Thread vincent gromakowski 
I am looking for way to optimize large reads.
I have seen using SSD is a good option but out of budget, so I am looking
for a way to use some kind of tiering with few SSD caching hot data from
HDD.
I have identified two solutions and would like to get opinions from you and
if you have any experience using them:
- use ZFS with L2ARC functionality
- use Rapiddisk/Rapidcache Linux kernel module
Any opinion ? Constraints ? REX ?
Thanks