Filestore had no such recommendation for size of journal per TB. The default was a flat 10GB partition. For bluestore, the recommendation has been 10GB per TB. However, with your setup, I would probably bump that up a bit more just to give you more room for your WAL/DB partition. While bluestore _can_ spill over to the spinning disk, it will slow your speeds and create performance issues that may be hard to track down.
On Wed, Mar 21, 2018 at 6:38 AM Ján Senko <jan.senko@xxxxxxxxx> wrote:
2018-03-21 8:56 GMT+01:00 Caspar Smit <casparsmit@xxxxxxxxxxx>:2018-03-21 7:20 GMT+01:00 ST Wong (ITSC) <ST@xxxxxxxxxxxxxxxx>:Hi all,
We got some decommissioned servers from other projects for setting up OSDs. They’ve 10 2TB SAS disks with 4 2TB SSD.
We try to test with bluestores and hope to play wal and db devices on SSD. Need advice on some newbie questions:
1. As there are more SAS than SSD, is it possible/recommended to put wal and db of multiple OSDs in partitions on same SSD (instead of using whole SSD device) ?
Yes, that's common practice. Although the general advice is no more then 5 OSD's per wal/db SSD.I understand this was general advice in the FileStore era, because all writes had to go through journal first.However IIRC in BlueStore only some writes need to go to db? Is this number therefore different now?2. if ok to do 1., how to size the SSD partition for wal/db ?
~ 10GB per TB. In your case 20GB partitions for 2TB drives.Again, this was common for FileStore Journals. As we know BlueStore can live without separate db, and will store excess db on the drive itself. What is the current recommendation?
3. do we need to tune parameters like bluestore_cache_size_ssd when SSD is used in OSD?
Only if your low on RAM.Caspar
Thanks a lot.
Best Regards,
/ST Wong
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