Re: Impact of fancy striping

[nicolasc <nicolas.canceill@xxxxxxxxxxx>]

Hi Kyle,

All OSDs are SATA drives in JBOD. The journals are all on a pair of SAS in RAID0. All of those are on a shared backplane with a single RAID controller (8 ports -> 12 disks).

I also have a pair of SAS in RAID1 holding the OS, which may be on a different port/data-path. I am going to try and put the journals there, and see how that goes. Thank you for this answer, Kyle.

Once again, every solution to my fancy striping problems is about the journal settings. I agree, my journal setup is not optimal, but I would really appreciate it if someone could:
- explain why the journal setup is way more important than striping settings;
- give me hints about fancy striping itself, and about how to make it work with XFS on RBD.

Best regards,

Nicolas Canceill
Scalable Storage Systems
SURFsara (Amsterdam, NL)

On 12/01/2013 12:47 AM, Kyle Bader wrote:

> This journal problem is a bit of wizardry to me, I even had weird intermittent issues with OSDs not starting because the journal was not found, so please do not hesitate to suggest a better journal setup.

You mentioned using SAS for journal, if your OSDs are SATA and a expander is in the data path it might be slow from MUX/STP/etc overhead. If the setup is all SAS you might try collocating the journal with it's matching data partition on a single disk. Two spindles must be contended with 9 OSDs. How are your drives attached?

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