On Thu, Apr 12, 2012 at 5:05 PM, Leen Besselink <leen@xxxxxxxxxxxxxxxxx> wrote: > (I've been lurking the mailinglist archive for a few months already, I think > bcache sounds really interresting) > > Hello Joseph, > >> Carrying out some scalability tests on high I/O systems. More tests to >> come using the Phoronix Test Suite. >> >> Fio summary: >> 24 jobs >> Direct IO >> Randwrite test >> Total of about 80k IOPs at 3.5k IOPS per thread. >> >> Test rig specs: >> 2x Intel(R) Xeon(R) CPU X5650 @ 2.67GHz (12 physical cores, 24 logical) >> 12x 2TB Seagate nearline-SAS in RAID6 on LSI Logic / Symbios Logic LSI >> MegaSAS 9260 >> 2x Intel 520 SSDs 120GB in RAID0 >> >> The 2 520s are striped with md raid as /dev/md0 whch is formatted as a >> bcache cache device using 1M buckets and 8k hard block size >> Backing device is the big old raid6. >> >> Random IO performance of the native raid0 is about 96K IOPs, backing >> device in the realm of 1600ish. >> However the backing device has a sequential IO performance of about 1.5GB/s. >> > > So why do you put your SSDs in RAID0 ? > > If you are using RAID6 for your HDD you obviously care about your data, shouldn't > you be using RAID1 or let bcache do some RAID1-like behaviour* ? > > Because when you use RAID0 your data will only be written to one SSD. > > * I think bcache had some ability to handle that sort of automatically. That's been in the design since forever, but I haven't gotten around to finishing it since we haven't needed it internally. (But yes, the idea is to have multile SSDs in a cache set, with only dirty data and metadata mirrored. Wouldn't be a _huge_ amount of work to finish.) > >> Below are some quick findings using fio - showing very good >> scalability of bcache even with very very fast SSDs. >> *Note: The SSDs are connected via a SATA2 interface being somewhat of >> a bottleneck. > > Have a nice day, > Leen. > -- > To unsubscribe from this list: send the line "unsubscribe linux-bcache" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
