Re: Some RAID levels do not support bitmap
Neil Brown wrote: On Monday June 11, [EMAIL PROTECTED] wrote: Jan Engelhardt wrote: Hi, RAID levels 0 and 4 do not seem to like the -b internal. Is this intentional? Runs 2.6.20.2 on i586. (BTW, do you already have a PAGE_SIZE=8K fix?) 14:47 ichi:/dev # mdadm -C /dev/md0 -l 4 -e 1.0 -b internal -n 2 /dev/ram[01] mdadm: RUN_ARRAY failed: Input/output error mdadm: stopped /dev/md0 14:47 ichi:/dev # mdadm -C /dev/md0 -l 0 -e 1.0 -b internal -n 2 /dev/ram[01] mdadm: RUN_ARRAY failed: Cannot allocate memory mdadm: stopped /dev/md0 Right... md: bitmaps not supported for this level. Bitmaps show what data has been modified but not written. For RAID-0 there is no copy, therefore there can be no bitmap to show what still needs to be updated. I would have thought that RAID-4 would support bitmaps, but maybe it was just never added because use of RAID-4 is pretty uncommon. added late rather than never added. 2.6.21 supports bitmaps on RAID-4, The patch is about 2 lines and would apply to 2.6.20 with no trouble. http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=3d37890baa4ca962f8a6b77525b8f3d0698eee09 BTW: RAID-4 seems to work fine with an external bitmap. Were you trying to do internal? I suspect you were using 2.6.21-rc6 or later? No, the machine I had for trial was 2.6.15 with a few patches, none in RAID. Seemed to work just fine if I put the bitmap on an external device. Was that not as expected? -- bill davidsen [EMAIL PROTECTED] CTO TMR Associates, Inc Doing interesting things with small computers since 1979 - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Some RAID levels do not support bitmap
Hi, RAID levels 0 and 4 do not seem to like the -b internal. Is this intentional? Runs 2.6.20.2 on i586. (BTW, do you already have a PAGE_SIZE=8K fix?) 14:47 ichi:/dev # mdadm -C /dev/md0 -l 4 -e 1.0 -b internal -n 2 /dev/ram[01] mdadm: RUN_ARRAY failed: Input/output error mdadm: stopped /dev/md0 14:47 ichi:/dev # mdadm -C /dev/md0 -l 0 -e 1.0 -b internal -n 2 /dev/ram[01] mdadm: RUN_ARRAY failed: Cannot allocate memory mdadm: stopped /dev/md0 Right... md: bitmaps not supported for this level. Thanks, Jan -- - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Some RAID levels do not support bitmap
Jan Engelhardt wrote: Hi, RAID levels 0 and 4 do not seem to like the -b internal. Is this intentional? Runs 2.6.20.2 on i586. (BTW, do you already have a PAGE_SIZE=8K fix?) 14:47 ichi:/dev # mdadm -C /dev/md0 -l 4 -e 1.0 -b internal -n 2 /dev/ram[01] mdadm: RUN_ARRAY failed: Input/output error mdadm: stopped /dev/md0 14:47 ichi:/dev # mdadm -C /dev/md0 -l 0 -e 1.0 -b internal -n 2 /dev/ram[01] mdadm: RUN_ARRAY failed: Cannot allocate memory mdadm: stopped /dev/md0 Right... md: bitmaps not supported for this level. Bitmaps show what data has been modified but not written. For RAID-0 there is no copy, therefore there can be no bitmap to show what still needs to be updated. I would have thought that RAID-4 would support bitmaps, but maybe it was just never added because use of RAID-4 is pretty uncommon. BTW: RAID-4 seems to work fine with an external bitmap. Were you trying to do internal? -- bill davidsen [EMAIL PROTECTED] CTO TMR Associates, Inc Doing interesting things with small computers since 1979 - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
