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From Ran User <ranuse...@gmail.com>
Subject Re: idea drive layout - 4 drives + RAID question
Date Thu, 01 Nov 2012 08:16:57 GMT
Thanks.  Yep, I think OS + CL (2 drive RAID1) will provide the best balance
of reduced headaches / performance.  I'll also be pondering 1 drive OS, 1
drive CL as well.
On Wed, Oct 31, 2012 at 9:27 PM, aaron morton <aaron@thelastpickle.com>wrote:

> Good question.
>
> The is a comment on the DS blog or docs somewhere that says on EC2 running
> the commit log on the raid-0 ephemeral is preferred. I think the
> recommendation was specifically about how the disks are setup on EC2.
>
> While the commit log will be competing with logs and everything else on
> the OS volume, it would be competing with C* reads, Memtable flushing,
> compacting and repairing on the data volume.
>
> The only way to be sure is to test both setups.
>
> Cheers
>
> -----------------
> Aaron Morton
> Freelance Developer
> @aaronmorton
> http://www.thelastpickle.com
>
> On 31/10/2012, at 1:11 PM, Ran User <ranuser99@gmail.com> wrote:
>
> Is there a concern of a large falloff in commit log write performance
> (sequential) when sharing 2 drives (RAID 1) with the OS (os and services
> writing their own logs, etc)?  Do you expect the hit to be marginal?
>
>
> On Tue, Oct 30, 2012 at 7:58 PM, aaron morton <aaron@thelastpickle.com>wrote:
>
>> We also have 4-disk nodes, and we use the following layout:****
>> 2 x OS + Commit in RAID 1****
>> 2 x Data disk in RAID 0
>>
>> +1
>>
>> You are replicating data at the application level and want the fastest
>> possible IO performance per node.
>>
>>  You can already distribute the
>> individual Cassandra column families on different drives by just
>> setting up symlinks to the individual folders.
>>
>> There are some features coming in 1.2 that make using a JBOD setup
>> easier.
>>
>> Cheers
>>
>>  -----------------
>> Aaron Morton
>> Freelance Developer
>> @aaronmorton
>> http://www.thelastpickle.com
>>
>> On 30/10/2012, at 9:23 PM, Pieter Callewaert <
>> pieter.callewaert@be-mobile.be> wrote:
>>
>> We also have 4-disk nodes, and we use the following layout:****
>> 2 x OS + Commit in RAID 1****
>> 2 x Data disk in RAID 0****
>>
>> This gives us the advantage we never have to reinstall the node when a
>> drive crashes.****
>>
>> Kind regards,****
>> Pieter****
>>
>>
>> *From:* Ran User [mailto:ranuser99@gmail.com]
>> *Sent:* dinsdag 30 oktober 2012 4:33
>> *To:* user@cassandra.apache.org
>> *Subject:* Re: idea drive layout - 4 drives + RAID question****
>>
>> Have you considered running RAID 10 for the data drives to improve MTBF?
>> ****
>>  ****
>> On one hand Cassandra is handling redundancy issues, on the other
>> hand, reducing the frequency of dealing with failed nodes
>> is attractive if cheap (switching RAID levels to 10). ****
>>  ****
>>
>> We have no experience with software RAID (have always used hardware raid
>> with BBU).  I'm assuming software RAID 1 or 10 (the mirroring part) is
>> inherently reliable (perhaps minus some edge case).****
>> On Tue, Oct 30, 2012 at 1:07 AM, Tupshin Harper <tupshin@tupshin.com>
>> wrote:****
>>
>> I would generally recommend 1 drive for OS and commit log and 3 drive
>> raid 0 for data. The raid does give you good performance benefit, and it
>> can be convenient to have the OS on a side drive for configuration ease and
>> better MTBF.****
>>
>> -Tupshin****
>> On Oct 29, 2012 8:56 PM, "Ran User" <ranuser99@gmail.com> wrote:****
>> I was hoping to achieve approx. 2x IO (write and read) performance via
>> RAID 0 (by accepting a higher MTBF).****
>>  ****
>> Do believe the performance gains of RAID0 are much lower and/or are not
>> worth it vs the increased server failure rate?****
>>  ****
>> From my understanding, RAID 10 would achieve the read performance
>> benefits of RAID 0, but not the write benefits.  I'm also considering RAID
>> 10 to maximize server IO performance. ****
>>  ****
>> Currently, we're working with 1 CF.****
>>  ****
>>  ****
>>
>> Thank you****
>> On Mon, Oct 29, 2012 at 11:51 PM, Timmy Turner <timm.turn@gmail.com>
>> wrote:****
>> I'm not sure whether the raid 0 gets you anything other than headaches
>> should one of the drives fail. You can already distribute the
>> individual Cassandra column families on different drives by just
>> setting up symlinks to the individual folders.
>>
>> 2012/10/30 Ran User <ranuser99@gmail.com>:****
>> > For a server with 4 drive slots only, I'm thinking:
>> >
>> > either:
>> >
>> > - OS (1 drive)
>> > - Commit Log (1 drive)
>> > - Data (2 drives, software raid 0)
>> >
>> > vs
>> >
>> > - OS  + Data (3 drives, software raid 0)
>> > - Commit Log (1 drive)
>> >
>> > or something else?
>> >
>> > also, if I can spare the wasted storage, would RAID 10 for cassandra
>> data
>> > improve read performance and have no effect on write performance?
>> >
>> > Thank you!****
>> ** **
>>
>>
>>
>
>

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