Hi all!
During a few tests with a new replica configuration I have found a serious issue involving sequential writes with outstanding operations. I have used Starwind Virtual SAN v8.0.8730 on W2012R2
Here are my results using CrystalDiskMark. Note that the Sequential Write (Q= 32,T= 1) IO test is 128KiB per IO, while Sequential Write (T= 1) IO test is 1MiB per IO. There aren't any bottlenecks on physical storage due to the large L1 cache.
Scenario #1 10GB LSFS volume with 20GB L1 WB cache and WITHOUT replica configured. Good results.
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CrystalDiskMark 4.0.3 x64 (C) 2007-2015 hiyohiyo
Crystal Dew World : [ ... ]
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* MB/s = 1,000,000 bytes/s [SATA/600 = 600,000,000 bytes/s]
* KB = 1000 bytes, KiB = 1024 bytes
Sequential Read (Q= 32,T= 1) : 1504.296 MB/s
Sequential Write (Q= 32,T= 1) : 1122.517 MB/s Very good result
Random Read 4KiB (Q= 32,T= 1) : 136.157 MB/s [ 33241.5 IOPS]
Random Write 4KiB (Q= 32,T= 1) : 90.135 MB/s [ 22005.6 IOPS]
Sequential Read (T= 1) : 1076.068 MB/s
Sequential Write (T= 1) : 655.435 MB/s
Random Read 4KiB (Q= 1,T= 1) : 25.029 MB/s [ 6110.6 IOPS]
Random Write 4KiB (Q= 1,T= 1) : 24.109 MB/s [ 5886.0 IOPS]
Test : 8192 MiB [P: 0.8% (0.1/10.0 GiB)] (x9)
Date : 2016/01/14 10:00:42
OS : Windows Server 2012 R2 [6.3 Build 9600] (x64)
Scenario #2 10GB LSFS volume with 20GB L1 WB cache and with replica configured and synchorized. Bad results.
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CrystalDiskMark 4.0.3 x64 (C) 2007-2015 hiyohiyo
Crystal Dew World : [ ... ]
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* MB/s = 1,000,000 bytes/s [SATA/600 = 600,000,000 bytes/s]
* KB = 1000 bytes, KiB = 1024 bytes
Sequential Read (Q= 32,T= 1) : 980.588 MB/s
Sequential Write (Q= 32,T= 1) : 14.287 MB/s !!!!! Why??????
Random Read 4KiB (Q= 32,T= 1) : 122.178 MB/s [ 29828.6 IOPS]
Random Write 4KiB (Q= 32,T= 1) : 74.826 MB/s [ 18268.1 IOPS] --> Good result, there is not any network latency or bandwith issue for this value
Sequential Read (T= 1) : 992.622 MB/s
Sequential Write (T= 1) : 130.435 MB/s --> Good result, there is not any network latency or bandwith issue for this value
Random Read 4KiB (Q= 1,T= 1) : 24.311 MB/s [ 5935.3 IOPS]
Random Write 4KiB (Q= 1,T= 1) : 5.279 MB/s [ 1288.8 IOPS]
Test : 8192 MiB [P: 0.8% (0.1/10.0 GiB)] (x9)
Date : 2016/01/14 10:30:13
OS : Windows Server 2012 R2 [6.3 Build 9600] (x64)
Scenario #3 10GB LSFS volume with 20GB L1 WB cache and with replica removed from replication manager while configured. Still bad results.
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CrystalDiskMark 4.0.3 x64 (C) 2007-2015 hiyohiyo
Crystal Dew World : [ ... ]
-----------------------------------------------------------------------
* MB/s = 1,000,000 bytes/s [SATA/600 = 600,000,000 bytes/s]
* KB = 1000 bytes, KiB = 1024 bytes
Sequential Read (Q= 32,T= 1) : 837.927 MB/s
Sequential Write (Q= 32,T= 1) : 30.132 MB/s !!!!! Why this bad value?????? There is no network activity!!
Random Read 4KiB (Q= 32,T= 1) : 5.656 MB/s [ 1380.9 IOPS]
Random Write 4KiB (Q= 32,T= 1) : 94.785 MB/s [ 23140.9 IOPS] --> Better result because there is no network activity
Sequential Read (T= 1) : 50.536 MB/s
Sequential Write (T= 1) : 307.899 MB/s --> Better result because there is no network activity
Random Read 4KiB (Q= 1,T= 1) : 0.522 MB/s [ 127.4 IOPS]
Random Write 4KiB (Q= 1,T= 1) : 15.577 MB/s [ 3803.0 IOPS]
Test : 8192 MiB [P: 0.8% (0.1/10.0 GiB)] (x9)
Date : 2016/01/14 10:42:02
OS : Windows Server 2012 R2 [6.3 Build 9600] (x64)
Because this results I suspect that there is some software related problem managing large IOs while outstanding operations with a volume is configured as HA.
Any suggestion to get better results will be highly appreciated.
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