Hi James,
Thank you for this clarification. I am quite aware of that, which is why
the journals are on SAS disks in RAID0 (SSDs out of scope).
I still have trouble believing that fast-but-not-super-fast journals is
the main reason for the poor performances observed. Maybe I am mistaken?
Best regards,
Nicolas Canceill
Scalable Storage Systems
SURFsara (Amsterdam, NL)
On 12/03/2013 03:01 PM, James Pearce wrote:
I would really appreciate it if someone could:
- explain why the journal setup is way more important than striping
settings;
I'm not sure if it's what you're asking, but any write must be
physically written to the journal before the operation is
acknowledged. So the overall cluster performance (or rather write
latency) is always governed by the speed of those journals. Data is
then gathered up into (hopefully) larger blocks and committed to OSDs
later.
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