Mike Viau:
>> On Mon, 13 Dec 2010 21:46:59 +0100 <ml@well-adjusted.de> wrote:
>>
>> Partition 1 does not start on physical sector boundary.
>
> I don't understand the implied meaning of this error? Did you take any
> precautions as to the alignment of your partition? What about if you
> were planning on having multiple partitions?
The error says that the partition is not aligned to the physical sector
size which presumably incurs a performance penalty. When setting things
up, I chose not to care about that (didn't remember seeing such a
warning either).
>> I don't have a serious performance issue, though. There's an encrypted
>> LVM volume on top of it and throughput is limited by the CPU (Atom D510)
>> at about 20-25MByte/s. An unencrypted volume I just created for this
>> test yields 72MByte/s write and 98MByte/s read throughput on the RAID.
>
> That sounds decent,
ACK, I would just expect better read performance because of the
striping, but I don't really know much about RAIDs (it's my first) and I
mostly used the default settings.
> how are you achieving RAID 1 over 0 (10) though with three drives?
You can create RAID10 with three disks using mdadm. It's not exactly the
same as RAID1 over RAID0:
https://raid.wiki.kernel.org/index.php/Introduction#RAID-10
>> Just out of curiosity, I will try reformatting the drives and see
>> whether the results for unencrypted access change.
I just removed one of the WD10EARs from the RAID and used parted to
partition it:
(parted) print
Model: ATA WDC WD10EARS-22Y (scsi)
Disk /dev/sdc: 1953525168s
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Number Start End Size File system Name Flags
1 2048s 1953118384s 1953116337s primary
But now mdadm complains when re-adding the drive:
jigsaw kernel: [273468.958063] md: bind<sdc1>
jigsaw kernel: [273468.986186] md0: Warning: Device sdc1 is misaligned
Recovery speed appears to be the same as before, as far as I can
remember (after 16% of 1TB at 39MByte/s). Still not bad. The 72MB/s from
above were just a short test writing 500MB (including sync).
J.
--
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