On 08/31/2015 09:39 AM, Wido den Hollander wrote: > True, but your performance is greatly impacted during recovery. So a > three node cluster might work well when the skies are clear and the sun > is shining, but it has a hard time dealing with a complete node failure. The question of "how tiny a cluster can be" I answer with some perf. data I collected few days ago. My setup: - 3 armhf based servers (a sort of raspberrypi), - only one 100 mbit/s LAN for all sort of access, - 3 usb sticks with dedicated 4 GB /dev/sda1 partition sticked in each armhf server and formatted with xfs, - 3 MMC cards for OS, - OSD jornal on MMC, OSD on USB Stick - 1 ordinary PC as client, - 3 OSDs, 3 MONs, 1 MDS. - debian8, 64bit everywhere I/O Performance test command based on "time dd if=/dev/zero of=./test bs=1024k count=1024" revealed: 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 81.3964 s, 13.2 MB/s real 1m28.619s user 0m0.052s sys 0m1.724s Result: A creation of 1 GB zerobased file consumes ~1min 30 secs. >From my point of view it is possible to set poor's man fileserver cluster on home lan typical hardware (i.e. my switch is a soho DSL modem/router) with 3 low power servers powered by smartphone chips and 3 cheap USB sticks as data storage. It is not quick, but it works. It consumes tiny amount of electrical power (whole "farm" needs about 25W), it has no mechanical rotating parts. The cluster uses passive radiators only and produces almost no heat wave: no fans are needed at all. During very hot summer this year I did notice no temperature based failure at all. HW cost: about 800 euro. Hint: try to find a centera on EMC² webpage with that price :-) My question: how can I "damage" one of my OSDs in an intelligent way to test the cluster performance during recovery ? Cheers, Marcin. _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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