Hi, We have run multiple instances with the StorScor and yes there is a reason MSFT is doing it and mostly every big cloud vendor caps the drive max throughput. I am completely in alignment with your breakdown of the code and there is no confusion there as that is how I started to model the behavior in FIO. They are surely capping the reads when they do this e.g. 10% SEQ_WR , 90% RND_RD (mixed WL), you can see that your default b/w for 90% will close enough to 100% PURE RND_RD but still not apple to apple. Still following the same process using MSFT recipe, In storScor I can clearly see that 90%RND_RD b/w is not capped as per the capping of the SEQ_WR throughput. e.g. StorScor output. perfmon_physicaldisk_1_d:_disk_reads/sec : 6,173.32 <-------------RND_RD is not capped but will surely get impacted as its not pure RND_RD perfmon_physicaldisk_1_d:_disk_writes/sec : 18.49 <---------------SEQ_WR is capped based on the %/100*rd_throughput. Read Bytes % :91.25% <-------------------------------------------------------Tells me ~90% RND_RD Write Bytes %: 8.75% <----------------------------------------------------------Tells me ~10% SEQ_RD In case of FIO theRND_RD also get impacted with the rate capping. My simple question is : Is the above MSFT receipe to model the mixed workload with controlling the throuput in FIO possible? I tried what i can figure from the documentation and your feedback and looks like FIO has limitation in this front. On Thu, Jul 13, 2017 at 11:20 PM, Sitsofe Wheeler <sitsofe@xxxxxxxxx> wrote: > Hi, > > Over on https://github.com/Microsoft/StorScore/blob/master/recipes/write_impact_check.rcp > the reads *must* be being capped otherwise what purpose does > $read_tput_KBps have? See the following: > > # Run the workload once undisturbed as a baseline. > my %baseline = > test( %workload, description => "$desc Baseline" ); > > my $read_tput_KBps = $baseline{'MB/sec Total'} * 1000; > [...] > > # Run again, this time with an aggressor process injecting > # writes in the background. The aggressor is rate-limited > # to a fraction of the baseline read throughput. > foreach my $write_workload ( @write_workloads ) > { > [...] > > my $write_tput_KBps = > int ( ( $write_pct / 100 ) * $read_tput_KBps ); > > The comment explains where the read "cap" came from. Briefly the > StoreScore program seems to be doing this: > 1. Run DISKSPD briefly to find the random read throughput of the disk > and put this value into the prev_rand_read_tput variable. > 2. seq_write_tput = prev_rand_read_tput * 10 / 100. > 3. rand_read_tput = prev_rand_read_tput. > 4. Run a detached DISKSPD at the same time as 4 that does sequential > writes but with a throughput cap of seq_write_tput. > 6. Run a detached DISKSPD that does random writes but with a > throughput cap of rand_read_tput. > > This strikes me as different to what you were proposing: > a) You said: "I want fio to do 10% 'this' / 90% 'that'" > b) That StorScore program does: "100% of 'that' capped to what I've > 'previously measured that' can do, and 'this' capped to 10% of the > 'previously measured that'". > > "Previously measured" becomes fixed and won't be changing as the > subsequent DISKSPD processes are running. Further, the ratio in a) > isn't between the same things as the ratio in b) and the even the > ratio itself isn't the same! > > For example, in the StorScore program imagine the baseline is > 100MBytes/s. You start running 4. and 5. together and the DISKSPD > process at 4. immediately falls to 0 (e.g. the disk is weird and can't > do reads and writes simultaneously). That does not mean the step 5. > DISKSPD will limit its throughput to 0 and continues chugging away at > 10MBytes/s. Thus the ratio between the step 4 DISKSPD and the step 5 > DISKSPD quickly becomes 10:0. > > You would have to talk to Microsoft as to why their StoreScore recipe > was written the way it is but the comments do suggest it was > intentional. It's worth noting DISKSPD itself can't balance entire > running "jobs" against each other but as previously mentioned that's > not what the StorScore program you linked is trying to do anyway... > > On 13 July 2017 at 21:55, abhishek koundal <akoundal@xxxxxxxxx> wrote: >> Yes that is correct. >> So e.g. if you have RND_RD b/w 45MBps and had 10%SEQ_WR 90%RND_RD the >> write throughput will be: >> =10/100 *45MBs = ~4.5MB/s >> >> Now if you try to cap the write throughput (rate =5m) to this in >> Linux, the RND_RD also gets impacted and wont run to its full >> potential. >> >> In StorScor reads thread will not get capped and only writes thread >> will be capped, hence deliver the expected results. >> >> On Thu, Jul 13, 2017 at 1:33 PM, Sitsofe Wheeler <sitsofe@xxxxxxxxx> wrote: >>> Hey, >>> >>> My Perl is a bit rusty but look at how the write throughput is calculated: >>> >>> # Run again, this time with an aggressor process injecting >>> # writes in the background. The aggressor is rate-limited >>> # to a fraction of the baseline read throughput. >>> foreach my $write_workload ( @write_workloads ) >>> { >>> my ($write_pattern, $write_pct) = @$write_workload; >>> >>> my $write_tput_KBps = >>> int ( ( $write_pct / 100 ) * $read_tput_KBps ); >>> >>> So it is accounting for the fact that the write throughput will be >>> limited to a percentage of the read throughput. >>> >>> On 13 July 2017 at 20:02, abhishek koundal <akoundal@xxxxxxxxx> wrote: >>>> Hi, >>>> The main thing that i am trying to do is to model the storScor in >>>> linux enviornment >>>> (https://github.com/Microsoft/StorScore/blob/master/recipes/write_impact_check.rcp). >>>> So there you can control the rate of the of the writes as per the % >>>> that is required. While running that on windows i can see that i can >>>> have different BS and rate defined for the runs achieving expected >>>> output. >>>> >>>> In the above mentioned case the RND_RD will be unconstrained (i.e. >>>> full BW they can achieve) but writes will be slowed to x% of RND_RD. >>>> In fio when >>>> e.g. >>>> SEQ_WR 10% and RND_RD 90%, with seq_wr rate capped at 10% of rnd rd >>>> (if rnd_rd was 40m) >>>> [SEQ_WR] >>>> rate=4m >>>> bs=128K >>>> rw=write >>>> flow=9 >>>> [RND_RD] >>>> rate=40m >>>> bs=4k >>>> rw=randread >>>> flow=-1 >>>> When i run this the output that comes back shows that SEQ_WR b/w is >>>> capped ~ 4m but RND_RD also gets severely hit for the IOPS+BW as it >>>> tried to put the total BW under <45m>. I want that RND_RD doesn't need >>>> to be capped and should run to it closest potential like I am see in >>>> storScor. >>>> Really appreciate for the support and helping me understand the limitations. >>> >>> -- >>> Sitsofe | http://sucs.org/~sits/ > > -- > Sitsofe | http://sucs.org/~sits/ -- Life is too short for silly things so invest your time in some productive outputs!! -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
