Andrei Mikhailovsky <andrei at ...> writes: > > Hello guys, > > was wondering if it is a good idea to enable TRIM (mount option discard) on the ssd disks which are used for > either cache pool or osd journals? As far as the journals are concerned, isn't this irrelevant if you're assigning a block device to them (which I believe is recommended)? As there's no associated filesystem with which to use the "discard" mount option, nor call "fstrim". > > For performance, is it better to enable it or run fstrim with cron every once in a while? My belief is that for the journals you want to "under provision" the SSD - eg perhaps by creating a partition that is a fair bit smaller than the SSD itself, and using that as the journal. And for the OSD (whether or not it's part of a cache tier), which does have a filesystem, I noticed a significant performance deterioration when using the "discard" mount option versus occasionally running "fstrim". I have tried both BTRFS and XFS, and it was similar in both cases. That said, my understanding is that SATA 3.1 has some optimizations (queued TRIM) that should help reduce the negative effects of mounting with the "discard" option, but I can't confirm from experience as the chipsets on my systems don't support it. > > Thanks > > Andrei >
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