[DRBD-user] drbd write performance slow, per disk 40M/s by dd command

[Chris Dickson]

Try turning off disk-barrier and disk-flushes and see if that makes a
difference.

2012/4/25 feng zheng <zf5984599 at gmail.com>

> hi, dear all:
>
> When I use drbd, I found the write performance very slow, against
> testing without drbd module.
>
> 1. the environment:
> -) CentOS 5.6
> -) 2.6.18 kernel
> -) drbd 8.4.1
> -) drbd.conf：
> resource r0
> {
>    protocol B;
>
>    net
>    {
> max-buffers  8000;
> max-epoch-size 8000;
> sndbuf-size 512K;
>    }
>
>    disk
>    {
>  al-extents 3389;
>    }
>
>
>    on OSS211
>    {
>        device /dev/drbd0;
>        disk /dev/sdb1;
>        address 192.168.100.231:7788;
>        meta-disk internal;
>    }
>
>    on OSS213
>    {
>        device /dev/drbd0;
>        disk /dev/sde1;
>        address 192.168.100.213:7788;
>        meta-disk internal;
>    }
>
> }
>
>
> 2. Test scenario:
> *) without drbd module,
> dd to write 1G stream into one disk, which formatted to ext3:
> [para]# !echo
> echo 3 > /proc/sys/vm/drop_caches
> [para]# !dd
> dd if=/dev/zero of=test1 bs=1M count=1000 conv=fdatasync
> 1000+0 records in
> 1000+0 records out
> 1048576000 bytes (1.0 GB) copied, 10.9905 seconds, 95.4 MB/s
>
> *) with drbd module,
> dd 1G stream to the disk, which is ext3 too:
> [para]# cat /proc/drbd
> version: 8.4.1 (api:1/proto:86-100)
> GIT-hash: 91b4c048c1a0e06777b5f65d312b38d47abaea80 build by
> root at OSS213, 2012-04-16 21:38:36
>  0: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate B r-----
>    ns:1260036 nr:0 dw:1260036 dr:297 al:330 bm:0 lo:0 pe:0 ua:0 ap:0
> ep:1 wo:b oos:0
> [para]#
> [para]# dd if=/dev/zero of=test1 bs=1M count=1000 conv=fdatasync
> 1000+0 records in
> 1000+0 records out
> 1048576000 bytes (1.0 GB) copied, 26.7392 seconds, 39.2 MB/s
> [para]# cat /proc/drbd
> version: 8.4.1 (api:1/proto:86-100)
> GIT-hash: 91b4c048c1a0e06777b5f65d312b38d47abaea80 build by
> root at OSS213, 2012-04-16 21:38:36
>  0: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate B r-----
>
> All the upper test writing disk are same. From the upper result, if i
> use DRBD to test, the performance
> is 39 MB/s; while if i do not use, the performance is about 95M/s.
>
> 3. My question is:
> -) this write performance decays so large is normal or not?
> I had read the following from the DRBD website:
> "15.1. Hardware considerations:
> ....  A single, reasonably recent, SCSI or SAS disk will
> typically allow streaming writes of roughly 40MB/s to the single disk."
> But this is very slow.
>
> -）if this is not normal, how can i turn this? is the config file
> something not correct?
>
> thanks a lot
> BRs,
> feng
> _______________________________________________
> drbd-user mailing list
> drbd-user at lists.linbit.com
> http://lists.linbit.com/mailman/listinfo/drbd-user
>
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