On Fri, Apr 13, 2012 at 11:43:14AM +1000, Joseph Glanville wrote: > On 13 April 2012 10:05, 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. > > I used RAID0 to demonstrate bcache scaling to 80k IOPs, this was not a > production machine nor a production configuration. > OK, that explains it. > Yes, atleast somewhat. Bcache cache devices are structured into > cache-sets, which are groups of SSDs that form one logical cache which > you can attach multiple backing devices to. > This is different from RAID1 because only dirty data is mirrored. You > don't need redundant copies of your read cache but you care very much > that you don't lose writeback cache data. > This isn't fully fleshed out in bcache yet but all the infrastructure > is there, I am looking to doing some work on it soonish I have just > been busy with other things. Yes, only mirror the dirty data. That is what it was, now I remember. Good to know what the state of development is also. Thanks. > > > >> 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 > > Joseph. > > -- > Founder | Director | VP Research > Orion Virtualisation Solutions | www.orionvm.com.au | Phone: 1300 56 > 99 52 | Mobile: 0428 754 846 > -- > 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
