[lustre-discuss] separate SSD only filesystem including HDD

Andreas Dilger adilger at whamcloud.com
Fri Aug 31 13:54:21 PDT 2018

On Aug 31, 2018, at 09:31, Alexander I Kulyavtsev <aik at fnal.gov> wrote:
> Thanks, Andreas!
> I’m looking on similar configuration.
> Performance wise, is zfs or ldiskfs recommended on NVMe OSTs?
> We are comfortable with zfs on current HDD system, how much penalty we will pay for ldiskfs on NVMe?
> zfs overhead can be different for high IOPS with NVMe; are there numbers?

I think ldiskfs will normally have better performance, just by virtue of less overhead (smaller/less metadata, no checksums, no redundancy, etc).

 The main question these days, is whether the performance of ZFS is "good enough", and whether the features (checksums, online scrub, drive management, etc) outweigh the performance impact?

> On 8/31/18, 3:20 AM, "Andreas Dilger" <adilger at whamcloud.com> wrote:
>>    Just to confirm, there is only a single NVMe device in each server node, or there is a single server with 24 NVMe devices in it?
>>    Depending on what you want to use the NVMe storage for (e.g. very fast short-term scratch == burst buffer) it may be OK to just make a Lustre filesystem with each NVMe device a separate OST with no redundancy.  The failure rate for these devices is low, and adding redundancy will hurt performance.

Cheers, Andreas
Andreas Dilger
Principal Lustre Architect

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