|Subject:||Re: Alignment: XFS + LVM2|
|From:||Marc Caubet <mcaubet@xxxxxx>|
|Date:||Thu, 8 May 2014 11:12:32 +0200|
thanks for your answer.
Everything begins and ends with the workload.
Basically we are moving a lot of data :) It means, parallel large files (GBs) are being written and read all the time. Basically we have a batch farm with 3,5k cores processing jobs that are constantly reading and writing to the storage pools (4PBs). Only few pools (~5% of the total) contain small files (and only small files).
Haven't experienced this yet. But good to know thanks :)Â On the other hand, we do not use zfs
Actually the stripe size for each RAID6 is 256KB but we plan to increase some pools to 1MB for all their RAIDs. It will be in order to compare performance for pools containing large files and if this improves, we will apply it to the other systems in the future.
> The idea is to aggregate the above devices and show only 1 storage space.
When creating a nested stripe, the stripe unit of the outer stripe (LVM)
Great. Hence, if the RAID6 stripe size is 256k then the LVM should be defined with 256k as well, isn't it?
We receive several parallel writes all the time, and afaik filesystems with such write load benenfit from a larger log. 128M is the maximum log size.
So how XFS should be formatted then? As you specify, should be aligned with the LVM stripe, as we have a LV with 3 stripes then 256k*3 and sw=30?
Thanks a lot,
Marc Caubet Serrabou
PIC (Port d'InformaciÃ CientÃfica)
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