forked from vitalif/vitastor
Mirror afr.js from /vitalif/ceph-afr-calc
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mon/afr.js
116
mon/afr.js
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@ -1,31 +1,16 @@
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// Functions to calculate Annualized Failure Rate of your cluster
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// if you know AFR of your drives, number of drives, expected rebalance time
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// and replication factor
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// License: VNPL-1.0 (see README.md for details)
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const { sprintf } = require('sprintf-js');
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// License: VNPL-1.0 (see https://yourcmc.ru/git/vitalif/vitastor/src/branch/master/README.md for details) or AGPL-3.0
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// Author: Vitaliy Filippov, 2020+
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module.exports = {
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cluster_afr_fullmesh,
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failure_rate_fullmesh,
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cluster_afr,
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print_cluster_afr,
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c_n_k,
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};
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print_cluster_afr({ n_hosts: 4, n_drives: 6, afr_drive: 0.03, afr_host: 0.05, capacity: 4000, speed: 0.1, replicas: 2 });
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print_cluster_afr({ n_hosts: 4, n_drives: 3, afr_drive: 0.03, capacity: 4000, speed: 0.1, replicas: 2 });
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print_cluster_afr({ n_hosts: 4, n_drives: 3, afr_drive: 0.03, afr_host: 0.05, capacity: 4000, speed: 0.1, replicas: 2 });
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print_cluster_afr({ n_hosts: 4, n_drives: 3, afr_drive: 0.03, capacity: 4000, speed: 0.1, ec: [ 2, 1 ] });
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print_cluster_afr({ n_hosts: 4, n_drives: 3, afr_drive: 0.03, afr_host: 0.05, capacity: 4000, speed: 0.1, ec: [ 2, 1 ] });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, capacity: 8000, speed: 0.02, replicas: 2 });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, afr_host: 0.05, capacity: 8000, speed: 0.02, replicas: 2 });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, capacity: 8000, speed: 0.02, replicas: 3 });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, afr_host: 0.05, capacity: 8000, speed: 0.02, replicas: 3 });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, capacity: 8000, speed: 0.02, replicas: 3, pgs: 100 });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, afr_host: 0.05, capacity: 8000, speed: 0.02, replicas: 3, pgs: 100 });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, afr_host: 0.05, capacity: 8000, speed: 0.02, replicas: 3, pgs: 100, degraded_replacement: 1 });
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/******** "FULL MESH": ASSUME EACH OSD COMMUNICATES WITH ALL OTHER OSDS ********/
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// Estimate AFR of the cluster
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@ -56,93 +41,38 @@ function failure_rate_fullmesh(n, a, f)
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/******** PGS: EACH OSD ONLY COMMUNICATES WITH <pgs> OTHER OSDs ********/
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// <n> hosts of <m> drives of <capacity> GB, each able to backfill at <speed> GB/s,
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// <k> replicas, <pgs> unique peer PGs per OSD
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// <k> replicas, <pgs> unique peer PGs per OSD (~50 for 100 PG-per-OSD in a big cluster)
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//
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// For each of n*m drives: P(drive fails in a year) * P(any of its peers fail in <l*365> next days).
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// More peers per OSD increase rebalance speed (more drives work together to resilver) if you
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// let them finish rebalance BEFORE replacing the failed drive.
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// let them finish rebalance BEFORE replacing the failed drive (degraded_replacement=false).
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// At the same time, more peers per OSD increase probability of any of them to fail!
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// osd_rm=true means that failed OSDs' data is rebalanced over all other hosts,
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// not over the same host as it's in Ceph by default (dead OSDs are marked 'out').
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//
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// Probability of all except one drives in a replica group to fail is (AFR^(k-1)).
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// So with <x> PGs it becomes ~ (x * (AFR*L/365)^(k-1)). Interesting but reasonable consequence
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// is that, with k=2, total failure rate doesn't depend on number of peers per OSD,
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// because it gets increased linearly by increased number of peers to fail
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// and decreased linearly by reduced rebalance time.
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function cluster_afr_pgs({ n_hosts, n_drives, afr_drive, capacity, speed, replicas, pgs = 1, degraded_replacement })
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function cluster_afr({ n_hosts, n_drives, afr_drive, afr_host, capacity, speed, ec, ec_data, ec_parity, replicas, pgs = 1, osd_rm, degraded_replacement, down_out_interval = 600 })
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{
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pgs = Math.min(pgs, (n_hosts-1)*n_drives/(replicas-1));
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const l = capacity/(degraded_replacement ? 1 : pgs)/speed/86400/365;
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return 1 - (1 - afr_drive * (1-(1-(afr_drive*l)**(replicas-1))**pgs)) ** (n_hosts*n_drives);
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}
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function cluster_afr_pgs_ec({ n_hosts, n_drives, afr_drive, capacity, speed, ec: [ ec_data, ec_parity ], pgs = 1, degraded_replacement })
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{
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const ec_total = ec_data+ec_parity;
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pgs = Math.min(pgs, (n_hosts-1)*n_drives/(ec_total-1));
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const l = capacity/(degraded_replacement ? 1 : pgs)/speed/86400/365;
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return 1 - (1 - afr_drive * (1-(1-failure_rate_fullmesh(ec_total-1, afr_drive*l, ec_parity))**pgs)) ** (n_hosts*n_drives);
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}
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// Same as above, but also take server failures into account
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function cluster_afr_pgs_hosts({ n_hosts, n_drives, afr_drive, afr_host, capacity, speed, replicas, pgs = 1, degraded_replacement })
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{
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let otherhosts = Math.min(pgs, (n_hosts-1)/(replicas-1));
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pgs = Math.min(pgs, (n_hosts-1)*n_drives/(replicas-1));
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let pgh = Math.min(pgs*n_drives, (n_hosts-1)*n_drives/(replicas-1));
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const ld = capacity/(degraded_replacement ? 1 : pgs)/speed/86400/365;
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const lh = n_drives*capacity/pgs/speed/86400/365;
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const p1 = ((afr_drive+afr_host*pgs/otherhosts)*lh);
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const p2 = ((afr_drive+afr_host*pgs/otherhosts)*ld);
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return 1 - ((1 - afr_host * (1-(1-p1**(replicas-1))**pgh)) ** n_hosts) *
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((1 - afr_drive * (1-(1-p2**(replicas-1))**pgs)) ** (n_hosts*n_drives));
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}
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function cluster_afr_pgs_ec_hosts({ n_hosts, n_drives, afr_drive, afr_host, capacity, speed, ec: [ ec_data, ec_parity ], pgs = 1, degraded_replacement })
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{
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const ec_total = ec_data+ec_parity;
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const otherhosts = Math.min(pgs, (n_hosts-1)/(ec_total-1));
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pgs = Math.min(pgs, (n_hosts-1)*n_drives/(ec_total-1));
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const pgh = Math.min(pgs*n_drives, (n_hosts-1)*n_drives/(ec_total-1));
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const ld = capacity/(degraded_replacement ? 1 : pgs)/speed/86400/365;
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const lh = n_drives*capacity/pgs/speed/86400/365;
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const p1 = ((afr_drive+afr_host*pgs/otherhosts)*lh);
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const p2 = ((afr_drive+afr_host*pgs/otherhosts)*ld);
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return 1 - ((1 - afr_host * (1-(1-failure_rate_fullmesh(ec_total-1, p1, ec_parity))**pgh)) ** n_hosts) *
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((1 - afr_drive * (1-(1-failure_rate_fullmesh(ec_total-1, p2, ec_parity))**pgs)) ** (n_hosts*n_drives));
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}
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// Wrapper for 4 above functions
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function cluster_afr(config)
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{
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if (config.ec && config.afr_host)
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{
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return cluster_afr_pgs_ec_hosts(config);
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}
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else if (config.ec)
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{
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return cluster_afr_pgs_ec(config);
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}
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else if (config.afr_host)
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{
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return cluster_afr_pgs_hosts(config);
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}
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else
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{
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return cluster_afr_pgs(config);
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}
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}
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function print_cluster_afr(config)
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{
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console.log(
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`${config.n_hosts} nodes with ${config.n_drives} ${sprintf("%.1f", config.capacity/1000)}TB drives`+
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`, capable to backfill at ${sprintf("%.1f", config.speed*1000)} MB/s, drive AFR ${sprintf("%.1f", config.afr_drive*100)}%`+
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(config.afr_host ? `, host AFR ${sprintf("%.1f", config.afr_host*100)}%` : '')+
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(config.ec ? `, EC ${config.ec[0]}+${config.ec[1]}` : `, ${config.replicas} replicas`)+
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`, ${config.pgs||1} PG per OSD`+
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(config.degraded_replacement ? `\n...and you don't let the rebalance finish before replacing drives` : '')
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);
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console.log('-> '+sprintf("%.7f%%", 100*cluster_afr(config))+'\n');
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const pg_size = (ec ? ec_data+ec_parity : replicas);
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pgs = Math.min(pgs, (n_hosts-1)*n_drives/(pg_size-1));
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const host_pgs = Math.min(pgs*n_drives, (n_hosts-1)*n_drives/(pg_size-1));
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const resilver_disk = n_drives == 1 || osd_rm ? pgs : (n_drives-1);
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const disk_heal_time = (down_out_interval + capacity/(degraded_replacement ? 1 : resilver_disk)/speed)/86400/365;
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const host_heal_time = (down_out_interval + n_drives*capacity/pgs/speed)/86400/365;
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const disk_heal_fail = ((afr_drive+afr_host/n_drives)*disk_heal_time);
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const host_heal_fail = ((afr_drive+afr_host/n_drives)*host_heal_time);
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const disk_pg_fail = ec
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? failure_rate_fullmesh(ec_data+ec_parity-1, disk_heal_fail, ec_parity)
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: disk_heal_fail**(replicas-1);
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const host_pg_fail = ec
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? failure_rate_fullmesh(ec_data+ec_parity-1, host_heal_fail, ec_parity)
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: host_heal_fail**(replicas-1);
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return 1 - ((1 - afr_drive * (1-(1-disk_pg_fail)**pgs)) ** (n_hosts*n_drives))
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* ((1 - afr_host * (1-(1-host_pg_fail)**host_pgs)) ** n_hosts);
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}
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/******** UTILITY ********/
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@ -0,0 +1,28 @@
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const { sprintf } = require('sprintf-js');
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const { cluster_afr } = require('./afr.js');
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print_cluster_afr({ n_hosts: 4, n_drives: 6, afr_drive: 0.03, afr_host: 0.05, capacity: 4000, speed: 0.1, replicas: 2 });
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print_cluster_afr({ n_hosts: 4, n_drives: 3, afr_drive: 0.03, afr_host: 0, capacity: 4000, speed: 0.1, replicas: 2 });
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print_cluster_afr({ n_hosts: 4, n_drives: 3, afr_drive: 0.03, afr_host: 0.05, capacity: 4000, speed: 0.1, replicas: 2 });
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print_cluster_afr({ n_hosts: 4, n_drives: 3, afr_drive: 0.03, afr_host: 0, capacity: 4000, speed: 0.1, ec: true, ec_data: 2, ec_parity: 1 });
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print_cluster_afr({ n_hosts: 4, n_drives: 3, afr_drive: 0.03, afr_host: 0.05, capacity: 4000, speed: 0.1, ec: true, ec_data: 2, ec_parity: 1 });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, afr_host: 0, capacity: 8000, speed: 0.02, replicas: 2 });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, afr_host: 0.05, capacity: 8000, speed: 0.02, replicas: 2 });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, afr_host: 0, capacity: 8000, speed: 0.02, replicas: 3 });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, afr_host: 0.05, capacity: 8000, speed: 0.02, replicas: 3 });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, afr_host: 0, capacity: 8000, speed: 0.02, replicas: 3, pgs: 100 });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, afr_host: 0.05, capacity: 8000, speed: 0.02, replicas: 3, pgs: 100 });
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print_cluster_afr({ n_hosts: 10, n_drives: 10, afr_drive: 0.1, afr_host: 0.05, capacity: 8000, speed: 0.02, replicas: 3, pgs: 100, degraded_replacement: 1 });
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function print_cluster_afr(config)
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{
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console.log(
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`${config.n_hosts} nodes with ${config.n_drives} ${sprintf("%.1f", config.capacity/1000)}TB drives`+
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`, capable to backfill at ${sprintf("%.1f", config.speed*1000)} MB/s, drive AFR ${sprintf("%.1f", config.afr_drive*100)}%`+
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(config.afr_host ? `, host AFR ${sprintf("%.1f", config.afr_host*100)}%` : '')+
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(config.ec ? `, EC ${config.ec_data}+${config.ec_parity}` : `, ${config.replicas} replicas`)+
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`, ${config.pgs||1} PG per OSD`+
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(config.degraded_replacement ? `\n...and you don't let the rebalance finish before replacing drives` : '')
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);
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console.log('-> '+sprintf("%.7f%%", 100*cluster_afr(config))+'\n');
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}
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