On Wed, Aug 31, 2011 at 4:56 PM, John Robinson
<john.robinson@xxxxxxxxxxxxxxxx> wrote:
> On 31/08/2011 13:30, Paul Clements wrote:
>>
>> On Wed, Aug 31, 2011 at 5:05 AM, CoolCold<coolthecold@xxxxxxxxx> wrote:
>>
>>>> root@gamma2:~# cat /proc/mdstat
>>>> Personalities : [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
>>>> md3 : active raid1 sdc3[1] sdb3[0]
>>>> 1443552640 blocks [2/2] [UU]
>>>> bitmap: 16/22 pages [64KB], 32768KB chunk
>>
>>> More details now:
>>> Array still has 16/22 dirty pages:
>>
>>> root@gamma2:~# mdadm --examine-bitmap /dev/sdc3
>>
>>> Sync Size : 1443552640 (1376.68 GiB 1478.20 GB)
>>> Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
>>
>> But only 189 bits dirty. This means the bits are just distributed
>> across the disk (which is why you have 16/22 pages dirty).
>>
>> Any activity on the disk? 189 bits could easily be explained by a
>> small amount of background disk activity on a disk that big.
>
> That makes sense to me. I have:
>
> $ cat /proc/mdstat
> Personalities : [raid6] [raid5] [raid4] [raid1]
> md1 : active raid6 sde2[4] sdd2[3] sdc2[2] sdb2[1] sda2[0]
> 2929966080 blocks level 6, 512k chunk, algorithm 2 [5/5] [UUUUU]
> bitmap: 2/4 pages [8KB], 131072KB chunk
>
> Oh no! Half my array is dirty! But then:
>
> # mdadm --examine-bitmap /dev/sdb2
> Filename : /dev/sdb2
> Magic : 6d746962
> Version : 4
> UUID : d8c57a89:166ee722:23adec48:1574b5fc
> Events : 1338800
> Events Cleared : 1338800
> State : OK
> Chunksize : 128 MB
> Daemon : 5s flush period
> Write Mode : Normal
> Sync Size : 976655360 (931.41 GiB 1000.10 GB)
> Bitmap : 7452 bits (chunks), 7 dirty (0.1%)
>
> Not so bad after all.
Makes sense, but...
>
> On the other hand, repeatedly checking /proc/mdstat shows different numbers
> of pages being dirty, and --examine-bitmap shows different numbers of bits
> being dirty each time, whereas CoolCold managed 16 pages repeatedly and 189
> bits being dirty twice in a row. CoolCold, please can you test
> --examine-bitmap again several times at least 5 seconds apart?
fast test with "sleep 5" reveals:
root@gamma2:~# for i in {1..20};do mdadm --examine-bitmap
/dev/sdc3|grep "Bitmap :";sleep 5;done
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
Bitmap : 44054 bits (chunks), 189 dirty (0.4%)
And 16/22 lasts for 4 days.
>
> Cheers,
>
> John.
>
>
--
Best regards,
[COOLCOLD-RIPN]
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