[Tfug] Really slow mdadm resyncing

Harry McGregor micros at osef.org
Sun Jun 17 23:35:30 MST 2007


Hi Matt,

It sounds like the drives are not in DMA mode.

Can you apt-get install hdparm and run the following:

To see if DMA mode is set run this:
hdparm /dev/hde
hdparm /dev/hdf

To do a basic benchmark on the drives, run this:
hdparm -tT /dev/hde
hdparm -tT /dev/hdf

                    Harry

Matt Jacob wrote:
> Hey guys:
>
> I just set up a box with Debian etch, and I'm using mdadm with 2 IDE
> drives in RAID1. I rsync'd about 50G of data to the box today, and
> that finished at around 9:00 or 10:00 this morning. More than twelve
> hours later, the RAID is still "active, resyncing", and I can't figure
> out why. I don't even know what that means (I thought the status was
> supposed to be "dirty" while recovering).
>
> Here's the output from mdadm:
>
> ned:~# mdadm -D /dev/md2
> /dev/md2:
>         Version : 00.90.03
>   Creation Time : Sat Jun 16 11:45:51 2007
>      Raid Level : raid1
>      Array Size : 159139776 (151.77 GiB 162.96 GB)
>     Device Size : 159139776 (151.77 GiB 162.96 GB)
>    Raid Devices : 2
>   Total Devices : 2
> Preferred Minor : 2
>     Persistence : Superblock is persistent
>
>     Update Time : Sat Jun 16 18:36:02 2007
>           State : active, resyncing
>  Active Devices : 2
> Working Devices : 2
>  Failed Devices : 0
>   Spare Devices : 0
>
>  Rebuild Status : 64% complete
>
>            UUID : 7f38bf9f:27f5bf50:05d2898a:691e38c1
>          Events : 0.9
>
>     Number   Major   Minor   RaidDevice State
>        0      33        3        0      active sync   /dev/hde3
>        1      33       67        1      active sync   /dev/hdf3
>
>
> And then there's this, which shows a pathetic 1M/s transfer rate:
>
> ned:~# cat /proc/mdstat
> Personalities : [raid1]
> md2 : active raid1 hde3[0] hdf3[1]
>       159139776 blocks [2/2] [UU]
>       [============>........]  resync = 64.3% (102406080/159139776)
> finish=830.1min speed=1137K/sec
>
> md1 : active raid1 hde2[0] hdf2[1]
>       746944 blocks [2/2] [UU]
>
> md0 : active raid1 hde1[0] hdf1[1]
>       192640 blocks [2/2] [UU]
>
> unused devices: <none>
>
>
> The strange thing is that my speed_limit_min is set to 50000, which
> should be 50M/s:
>
> ned:~# cat /proc/sys/dev/raid/speed_limit_min
> 50000
>
> Any ideas? Am I missing something? If I can't get better performance
> out of this thing, I'm gonna go back to my poor man's RAID which
> consisted of a nightly rsync job between the two drives.
>
> Matt
>
> P.S. Here are my system specs: Athlon 1200 MHz, 768 M RAM, (2) IDE ATA100 drives
>
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