LinearTapeFileSystem/ltfs

Read performance - ok / optimal

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#242 opened on Jan 31, 2021

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Description

I see there's another issue about read performance but that seems to be about a specific bug / environment so I'll create a new one.

Using M8 media in an HPE LTO8 autoloader, what is considered the best possible read performance currently? I'm seeing around 275-280 MB/s writes, which is very close to my raw tape speed, and 210 MB/s reads (+/- 10 MB/s). 210 MB/s is fine, but as always faster would be better. I'm using the latest master in Debian 10 on a xeon 2155 , 256 GB RAM and enterprise nvme drives. The files on the tape are 50-500 MB and I've tried using ltfs_ordered_copy and my own file copier with about the same result.

Is this the expected speed, or is there something I can do to improve it?

Contributor guide

Research direction
Examine the read path in the LTFS source code, focusing on buffer sizes, block alignment, and system call overhead. Compare with write path optimizations.
Tech stack
c
Domain
backend
Issue type
Performance
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
LinuxC
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40