Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Also use oflag=direct in both tests and perform them a few times, sometimes
high speeds are the result of caching.
On Wed, Apr 25, 2012 at 10:35 AM, Chris Dickson <chrisd1100 at gmail.com>wrote:
> 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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