From: Mark Nelson <mark.nelson@inktank.com>
To: Sage Weil <sage@inktank.com>
Cc: Gandalf Corvotempesta <gandalf.corvotempesta@gmail.com>,
ceph-devel@vger.kernel.org
Subject: Re: flashcache
Date: Wed, 16 Jan 2013 15:55:13 -0600 [thread overview]
Message-ID: <50F721C1.8070200@inktank.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1301161342580.27925@cobra.newdream.net>
On 01/16/2013 03:46 PM, Sage Weil wrote:
> On Wed, 16 Jan 2013, Gandalf Corvotempesta wrote:
>> 2013/1/16 Sage Weil <sage@inktank.com>:
>>> This sort of configuration effectively bundles the disk and SSD into a
>>> single unit, where the failure of either results in the loss of both.
>>> From Ceph's perspective, it doesn't matter if the thing it is sitting on
>>> is a single disk, an SSD+disk flashcache thing, or a big RAID array. All
>>> that changes is the probability of failure.
>>
>> Ok, it will fail, but this should not be an issue, in a cluster like
>> ceph, right?
>> With or without flashcache or SSD, ceph should be able to handle
>> disks/nodes/osds failures on its own by replicating in real time to
>> multiple server.
>
> Exactly.
>
>> Should I worry about loosing data in case of failure? It should
>> rebalance automatically in case of failure with no data loss.
>
> You should not worry, except to the extent that 2 might fail
> simultaneously, and failures in general are not good things.
>
>>> I would worry that there is a lot of stuff piling onto the SSD and it may
>>> become your bottleneck. My guess is that another 1-2 SSDs will be a
>>> better 'balance', but only experiementation will really tell us that.
>>>
>>> Otherwise, those seem to all be good things to put on teh SSD!
>>
>> I can't add more than 2 SSD, I don't have enough space.
>> I can move OS to the first 2 spinning disks in raid1 software, if this
>> will improve performance of SSD
>>
>> What about swap? I'm thinking to no use swap at all and start with
>> 16/32GB RAM
>
> You could use the first (single) disk for os and logs. You might not even
> bother with raid1, since you will presumably be replicating across hosts.
> When the OSD disk dies, you can re-run your chef/juju/puppet rule or
> whatever provisioning tool is at work to reinstall/configure the OS disk.
> The data on the SSDs and data disks will all be intact.
Other options might be network boot or even usb stick boot.
>
> sage
> --
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next prev parent reply other threads:[~2013-01-16 21:55 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-16 21:22 flashcache Gandalf Corvotempesta
2013-01-16 21:29 ` flashcache Sage Weil
2013-01-16 21:42 ` flashcache Gandalf Corvotempesta
2013-01-16 21:46 ` flashcache Sage Weil
2013-01-16 21:55 ` Mark Nelson [this message]
2013-01-16 21:59 ` flashcache Gandalf Corvotempesta
2013-01-16 21:57 ` flashcache Gandalf Corvotempesta
2013-01-16 21:53 ` flashcache Mark Nelson
2013-01-16 22:04 ` flashcache Gandalf Corvotempesta
2013-01-17 5:47 ` flashcache Stefan Priebe - Profihost AG
2013-01-17 13:34 ` flashcache Mark Nelson
2013-01-17 9:46 ` flashcache Gandalf Corvotempesta
2013-01-17 13:32 ` flashcache Joseph Glanville
2013-01-17 13:37 ` flashcache Mark Nelson
2013-01-17 13:44 ` flashcache Gandalf Corvotempesta
2013-01-17 14:30 ` flashcache Atchley, Scott
2013-01-17 14:48 ` flashcache Gandalf Corvotempesta
2013-01-17 15:00 ` flashcache Atchley, Scott
2013-01-17 15:07 ` flashcache Andrey Korolyov
2013-01-17 15:47 ` flashcache Atchley, Scott
2013-01-17 16:39 ` flashcache Andrey Korolyov
2013-01-20 2:56 ` flashcache Joseph Glanville
2013-01-21 23:57 ` flashcache John Nielsen
2013-01-30 20:10 ` flashcache Joseph Glanville
2013-01-17 15:14 ` flashcache Gandalf Corvotempesta
2013-01-17 15:50 ` flashcache Atchley, Scott
2013-01-17 16:01 ` flashcache Gandalf Corvotempesta
2013-01-17 16:12 ` flashcache Atchley, Scott
2013-01-17 16:19 ` flashcache Gandalf Corvotempesta
2013-01-22 21:06 ` flashcache Atchley, Scott
2013-01-22 21:08 ` flashcache Atchley, Scott
2013-01-17 16:20 ` flashcache Stefan Priebe
2013-01-17 16:21 ` flashcache Gandalf Corvotempesta
2013-01-17 16:24 ` flashcache Stefan Priebe
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