[ceph-users] Ceph or Gluster for implementing big NAS

Ashley Merrick singapore at amerrick.co.uk
Mon Nov 12 06:40:05 PST 2018


My 2 cents would be depends how H/A you need.

Going with the monster VM you have a single point of failure and a single
point of network congestion.

If you go the CephFS route you remove that single point of failure if you
mount to clients directly. And also can remove that single point of network
congestion.

Guess depends on the performance and uptime required , as I’d say that
could factory into your decisions.

On Mon, 12 Nov 2018 at 10:36 PM, Premysl Kouril <premysl.kouril at gmail.com>
wrote:

> Hi Kevin,
>
> I should have also said, that we are internally inclined towards the
> "monster VM" approach due to seemingly simpler architecture (data
> distribution on block layer rather than on file system layer). So my
> original question is more about comparing the two approaches (distribution
> on block layer vs distribution on filesystem layer). "Monster VM" approach
> being the one where we just keep mounting block volumes to a single VM
> with normal non-distributed filesystem and then exporting via NFS/CIFS.
>
> Regards,
> Prema
>
> On Mon, Nov 12, 2018 at 3:17 PM Kevin Olbrich <ko at sv01.de> wrote:
>
>> Hi Dan,
>>
>> ZFS without sync would be very much identical to ext2/ext4 without
>> journals or XFS with barriers disabled.
>> The ARC cache in ZFS is awesome but disbaling sync on ZFS is a very high
>> risk (using ext4 with kvm-mode unsafe would be similar I think).
>>
>> Also, ZFS only works as expected with scheduler set to noop as it is
>> optimized to consume whole, non-shared devices.
>>
>> Just my 2 cents ;-)
>>
>> Kevin
>>
>>
>> Am Mo., 12. Nov. 2018 um 15:08 Uhr schrieb Dan van der Ster <
>> dan at vanderster.com>:
>>
>>> We've done ZFS on RBD in a VM, exported via NFS, for a couple years.
>>> It's very stable and if your use-case permits you can set zfs
>>> sync=disabled to get very fast write performance that's tough to beat.
>>>
>>> But if you're building something new today and have *only* the NAS
>>> use-case then it would make better sense to try CephFS first and see
>>> if it works for you.
>>>
>>> -- Dan
>>>
>>> On Mon, Nov 12, 2018 at 3:01 PM Kevin Olbrich <ko at sv01.de> wrote:
>>> >
>>> > Hi!
>>> >
>>> > ZFS won't play nice on ceph. Best would be to mount CephFS directly
>>> with the ceph-fuse driver on the endpoint.
>>> > If you definitely want to put a storage gateway between the data and
>>> the compute nodes, then go with nfs-ganesha which can export CephFS
>>> directly without local ("proxy") mount.
>>> >
>>> > I had such a setup with nfs and switched to mount CephFS directly. If
>>> using NFS with the same data, you must make sure your HA works well to
>>> avoid data corruption.
>>> > With ceph-fuse you directly connect to the cluster, one component less
>>> that breaks.
>>> >
>>> > Kevin
>>> >
>>> > Am Mo., 12. Nov. 2018 um 12:44 Uhr schrieb Premysl Kouril <
>>> premysl.kouril at gmail.com>:
>>> >>
>>> >> Hi,
>>> >>
>>> >>
>>> >> We are planning to build NAS solution which will be primarily used
>>> via NFS and CIFS and workloads ranging from various archival application to
>>> more “real-time processing”. The NAS will not be used as a block storage
>>> for virtual machines, so the access really will always be file oriented.
>>> >>
>>> >>
>>> >> We are considering primarily two designs and I’d like to kindly ask
>>> for any thoughts, views, insights, experiences.
>>> >>
>>> >>
>>> >> Both designs utilize “distributed storage software at some level”.
>>> Both designs would be built from commodity servers and should scale as we
>>> grow. Both designs involve virtualization for instantiating "access virtual
>>> machines" which will be serving the NFS and CIFS protocol - so in this
>>> sense the access layer is decoupled from the data layer itself.
>>> >>
>>> >>
>>> >> First design is based on a distributed filesystem like Gluster or
>>> CephFS. We would deploy this software on those commodity servers and mount
>>> the resultant filesystem on the “access virtual machines” and they would be
>>> serving the mounted filesystem via NFS/CIFS.
>>> >>
>>> >>
>>> >> Second design is based on distributed block storage using CEPH. So we
>>> would build distributed block storage on those commodity servers, and then,
>>> via virtualization (like OpenStack Cinder) we would allocate the block
>>> storage into the access VM. Inside the access VM we would deploy ZFS which
>>> would aggregate block storage into a single filesystem. And this filesystem
>>> would be served via NFS/CIFS from the very same VM.
>>> >>
>>> >>
>>> >> Any advices and insights highly appreciated
>>> >>
>>> >>
>>> >> Cheers,
>>> >>
>>> >> Prema
>>> >>
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