[lustre-discuss] Data stored in OST

[Peter Grandi]

>>> On Mon, 22 May 2023 13:08:19 +0530, Nick dan via lustre-discuss <lustre-discuss at lists.lustre.org> said:

> Hi I had one doubt. In lustre, data is divided into stripes
> and stored in multiple OSTs. So each OST will have some part
> of data. My question is if one OST fails, will there be data
> loss?

This is extensively discussed in the Lustre manual with
comprehensive illustrations:

  https://doc.lustre.org/lustre_manual.xhtml#understandinglustre.storageio
  https://doc.lustre.org/lustre_manual.xhtml#pfl
  https://doc.lustre.org/lustre_manual.xhtml#understandingfailover

The usual practice is to use RAUD10 for the MDT(s) on
"enterprise" high-endurance SSD, and RAID6 for the OST on
"professional" mixed-load SSDs or "small" (1-2TB at most)
"datacenter" HDDs, fronted by failover-servers.

I personally think that is is best to rely on Lustre striping
and the "new" PFL LFR layout (across two OST "pools"), and have
each OST on a single device, and and very few OSTs per OSS, when
Lustre is used as "scratch" area for an HPC cluster.

  https://doc.lustre.org/lustre_manual.xhtml#flr