I've place the bitmap on an external EXT4 drive (1xHDD) but I would expect the file to be written too whenever data is changed on my RAID10 array, right?
I even did checksum of the bitmap file, and it's surely isn't changed.
Size of file is only 2KB (bitmap chunk-size is set to 64MB)
- I tried to stop and start the array, no change, no writing to the file
- If the file is not accessible when array starts I'll get the error
mdadm: Could not open bitmap file /mnt/1xHDD/R10_bitmap.datwhich is good
Check of bitmap file with
mdadm -X /mnt/1xHDD/R10_bitmap.dat
Filename : /mnt/1xHDD/R10_bitmap.dat Magic : 6d746962 Version : 4 UUID : 39f863d1:4d247162:c3672454:1765abe2 Events : 2914 Events Cleared : 2914 State : OK Chunksize : 64 MB Daemon : 5s flush period Write Mode : Normal Sync Size : 624877568 (595.93 GiB 639.87 GB) Bitmap : 9535 bits (chunks), 0 dirty (0.0%)
Content of my mdadm.conf:
HOMEHOST <system> MAILADDR root ARRAY /dev/md/SRV01:R10_HDD metadata=1.2 bitmap=/mnt/1xHDD/R10_bitmap.dat name=SRV01:R10_HDD UUID=39f863d1:4d247162:c3672454:1765abe2
By the way, any comments in regards to placing the bitmap file on a single HDD? Tried to just rename it and the array continues without problems, although
mdadm --details... will tell the bitmap has been deleted.
Additional note: Moving to external bitmap the write performance on this RAID10 array increased from 135MB/s to 370MB/s! (using direct IO, i.e. page-cache not in use).