On Sun, Jan 1, 2012 at 12:12 AM, Niels de Carpentier <ni...@decarpentier.com> wrote: >>> ... and depending on which SSD you use, it shouldn't matter. Really. >>> >>> Last time I tried with sandforce SSD + btrfs + -o discard, forcing >>> trim actually made things slower. Sandforce (and probably other modern >>> SSD) controllers can work just fine even without explicit trim fs >>> support. >> >> What command did you use to test this?
Normal usage, and some random i/o test tool like fio. >> >> I have an OCZ Agility 3 SSD, which have the latest Sandforce >> controller, so I would really like to try reproduce your test setup. Yours should be newer. Mine is somewhat-old corsair force 60 GB with btrfs on top. When I activated -o discard, it actually become slower. Also, when I used fstrim, the IOPS were capped at 100, so probably the slowdown is because of that (i.e. IOPS-limit of TRIM somewhere, possibly the controller) > > Ok, the sandforce controller makes things interesting. > > First of all, sandforce controllers have a very high failure rate, so make > sure you have backups!! Yes, but even knowing that I can't imagine going back to HDD for this particular system. It'd be too slow to bear :P > Sandforce controllers also use compression and deduplication to increase > performance. Encryption will make your data incompressible and random, so > this can have a big impact on performance, depending on the > characteristics of your data. In my case I use compress=lzo, so it shouldn't be compressible by the controllers. > Sandforce controllers also have life time throttling, which will throttle > writes heavily if it thinks you will wear out the flash within the > warranty period. If you have a very heavy write workload this can be an > issue. That's new. Is there a link/reference for that? > > If you don't have a working trim it is a good idea to leave part of your > drive unused. (Make sure you either do this after a full write erase of > the drive, or do a manual trim of that area, otherwise it won't work). > This will make sure the drive has enough spare sectors to do garbage > collection and can greatly improve performance if your drive is full. True. But on my last test I can't get fstrim to trim everything. It could only trim about 2GB out of 12GB free space. -- Fajar -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
