On Fri, 3 Jan 2020, Patrick Dung wrote: > Hello, > > A quick question on dm-integrity. Does dm-integrity layer honors fsync? Yes it does. However, it writes data into the journal and when the journal is flushed, it reports the fsync function as finished. On a mechanical disk, writes to contiguous space (i.e. the journal) are faster than random writes all over the disk, that's why you see better performance with dm-integrity than without it. Mikulas > I was testing dm-integrity and performance. It had a strange result that using dm-integrity with journal is faster than a normal file system or dm-integrity with > bitmap (no journal). fio is used for testing the storage performance. The device is a SATA hard disk drive. Then I created a 100GB partition for testing. > > Below is the test cases: > > 1) XFS on a partition directly test case > > 2) dm-integrity: crc32c on a partition with default setting journal commit interval is 10 seconds. Then create XFS on it. test case > > 3) dm-integrity: crc32c on a partition default setting journal commit interval set to 5 seconds. Then create XFS on it. > > 4) dm-integrity: crc32c on a partition default setting but using bitmap instead of journal. Then create XFS on it. > > FIO command: > > fio --filename=./t1 --direct=1 --rw=randrw --refill_buffers --norandommap --randrepeat=0 --ioengine=sync --bs=4k --rwmixread=75 --iodepth=16 --numjobs=8 --runtime=60 > --group_reporting --fsync=1 --name=4ktest --size=4G > > Result: > > 1. Read/Write IOPS: 117/41. Read/Write Speed 481KB/s 168KB/s > 2. Read/Write IOPS: 178/59. Read/Write Speed 732KB/s 244KB/s > 3. Read/Write IOPS: 169/57. Read/Write Speed 695KB/s 236KB/s > 4. Read/Write IOPS: 97/32. Read/Write Speed 400K/s 131KB/s > The original discussion in: https://gitlab.com/cryptsetup/cryptsetup/issues/513 . Milan Broz said the dm-devel mailing list is a suitable place to discuss the probem. > > Thanks in advance. > > Patrick > >
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