Hi All, I am trying to match the WRITE throughput for 512K chunk size to WRITE throughput I am getting with 32K chunk size. I am using dm-crypt module. My setup is : iozone (4k rec) -> ext4 -> dm-crypt dev mapper + raid5 (4 disks). In my past experience 512K chunk size was not very off from 32K chunk size on kernel 2.6.32 for above situation. >From iostats it seems that 512K is slow because of higher rrqm/s on the physical disks behind raid5 device (last 4 columns are from iostat -x on physical disks behind raid5) Chunk-size iozon MB/s Avgrq-sz r/s rMB/s rrqm/s 512K 25 MBps 976 ~60 ~7.00 ~1800 32K 39 MBps 63 ~20 ~0.55 ~100 Question: Is it that partial stripe happening and causing more reads here ? Question: Can someone suggest some code hacks or config changes such that even with 512K iozone writes to ext4/dm-crypt/raid5 device is close to 39 MBps? Or otherwise more pointers into code to understand and conclude will be helpful Question: Are the changes in dm-crypt or block layer (since 2.6.32) causing higher r/s rMB/s rrqm/s etc. ? How to tune it now? Question:MY hardware-crypto-offload modules receives nbytes=512bytes in aes_crypt_cbc (could not find ways to bump these nbytes more than 512). Are their ways to bump this number ? To compare here are same numbers (lower rrqm/s) if I remove dm-crypt : Chunk-size iozon MB/s Avgrq-sz r/s rMB/s rrqm/s 512K 81 MBps 976 ~12 ~0.41 ~100 32K 89 MBps 63 ~01 ~0.04 ~4 Quesiton: Why dm-crypt causing higher r/s rMB/s rrqm/s ( higher these lower write MB/s) ? regards rh -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
