Hi, Josh: Thanks for your reply. However, I had asked a question about replica setting before. http://www.spinics.net/lists/ceph-devel/msg07346.html If the performance of rbd device is n MB/s under replica=2, then that means the total io throughputs on hard disk is over 3 * n MB/s. Because I think the total number of copies is 3 in original. So, it seems not correct now, the total number of copies is only 2. The total io through puts on disk should be 2 * n MB/s. Right? -----Original Message----- From: Josh Durgin [mailto:josh.durgin@xxxxxxxxxxx] Sent: Tuesday, July 31, 2012 1:56 PM To: Eric YH Chen/WYHQ/Wiwynn Cc: ceph-devel@xxxxxxxxxxxxxxx; Chris YT Huang/WYHQ/Wiwynn; Victor CY Chang/WYHQ/Wiwynn Subject: Re: High-availability testing of ceph On 07/30/2012 07:46 PM, Eric_YH_Chen@xxxxxxxxxx wrote: > Hi, all: > > I am testing high-availability of ceph. > > Environment: two servers, and 12 hard-disk on each server. Version: Ceph 0.48 > Kernel: 3.2.0-27 > > We create a ceph cluster with 24 osd. > Osd.0 ~ osd.11 is on server1 > Osd.12 ~ osd.23 is on server2 > > The crush rule is using default rule. > rule rbd { > ruleset 2 > type replicated > min_size 1 > max_size 10 > step take default > step chooseleaf firstn 0 type host > step emit > } > > pool 2 'rbd' rep size 2 crush_ruleset 2 object_hash rjenkins pg_num > 1536 pgp_num 1536 last_change 1172 owner 0 > > Test case 1: > 1. Create a rbd device and read/write to it 2. Random turn off one osd > on server1 (service ceph stop osd.0) 3. check the read/write of rbd > device > > Test case 2: > 1. Create a rbd device and read/write to it 2. Random turn off one osd > on server1 (service ceph stop osd.0) 2. Random turn off one osd on > server2 (service ceph stop osd.12) 3. check the read/write of rbd > device > > About test case 1, we can access the rbd device as normal. But about test case 2, we would hang there and no response. > Is it a correct scenario ? > > I imagine that we can turn off any two osd when we set the replication as 2. > Because without the master data, we have two other copies on two different osd. > Even when we turn off two osd, we can find the data on third osd. > Any misunderstanding? Thanks! rep size is the total number of copies, so stopping two osds with rep size 2 may cause you to lose access to some objects. Josh -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
