[lustre-discuss] Is there aceiling of lustre filesystem a client can mount

Mark Hahn hahn at mcmaster.ca
Thu Jul 16 00:00:28 PDT 2020


> On Jul 15, 2020, at 12:29 AM, ??? <guru.novice at gmail.com> wrote:
>> Is there a ceiling for a Lustre filesystem that can be mounted in a cluster?

It is very high, as Andreas said.

>> If so, what's the number?

The following contains specific limits:

https://build.whamcloud.com/job/lustre-manual//lastSuccessfulBuild/artifact/lustre_manual.xhtml#idm140436304680016

You'll notice that you must assume some aspects of configuration, such as the
size and number of your OSTs.  I see OSTs in the range of 75-400TB (and OST
counts between 58 and 187).

>> If not, how much is proper?

Lustre is designed to scale.  So a config with a small number of OSTs,
on very few OSSes doesn't make that much sense.  OSTs are pretty much
expected to be decent-sized RAIDs.  There would be tradeoffs among cost-
efficient disk sizes (maybe 16T today) and RAID overhead (usually N+2),
and how that trades off with bandwidth (HBA and OSS network).

>> Does mount multiple filesystems  can affect the stability of each file system or cause other problems?

My experience is that the main factor in reliability is device count,
rather than how the devices are organized.  For instance, if you
have more OSSes, you may get linearly nicer performance, but 
you also increase your chance of having components crash or fail.

The main reason for separate filesystems is usually that the MDS
(maybe MTD) can be a bottleneck.  But you can scale MDSes, instead.

regards, mark hahn.


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