> Currently the biggest HDD is 20TB.

According to news articles, HDDs up to 26TB are sampling. Mind you they’re SMR. 
 And for many applications having that much capacity behind a tired SATA 
interface is a serious bottleneck; I’ve seen deployments cap HDD size at 8TB 
because of this.  But I digress...

30TB SSDs (eg. Intel / Solidigm P5316) have been shipping for a while now.

> 1 exabyte means 50.000 OSD
> cluster(without replication or EC)
> AFAIK Cern did some tests using 5000 OSDs.

Bigbang III used 10800!  The CERN bigbang findings have been priceless 
contributions to Ceph scalability.

> I don't know any larger clusters than Cern’s.

The bigbangs were all transient I think.  I would expect that there are 
clusters even larger than CERN’s production deployment in certain organizations 
that don’t talk about them.

> So I am not saying it is impossible but it is very unlikely to grow a single 
> Ceph cluster to that size.

In high school I couldn’t imagine using all 48KB on an Apple ][

640KB ought to be enough for anyone (apocryphal) 

When I ran Dumpling 450x 3TB OSDs were among the larger clusters according to 
Inktank at the time.

Basically, never say never.


> Maybe you should search for alternatives, like hdfs which I
> know/worked with more than 50.000 HDDs without problems.

HDFS is a different beast FWIW.

> 
> On Mon, Jun 20, 2022 at 10:46 AM Arnaud M <arnaud.meauzo...@gmail.com> wrote:
>> 
>> Hello to everyone
>> 
>> I have looked on the internet but couldn't find an answer.
>> Do you know the maximum size of a ceph filesystem ? Not the max size of a
>> single file but the limit of the whole filesystem ?
>> 
>> For example a quick search on zfs on google output :
>> A ZFS file system can store up to *256 quadrillion zettabytes* (ZB).
>> 
>> I would like to have the same answer with cephfs.
>> 
>> And if there is a limit, where is this limit coded ? Is it hard-coded or is
>> it configurable ?
>> 
>> Let's say someone wants to have a cephfs up to ExaByte, would it be
>> completely foolish or would the system, given enough mds and servers and
>> everything needed, be usable ?
>> 
>> Is there any other limit to a ceph filesystem ?
>> 
>> All the best
>> 
>> Arnaud
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