| View previous topic :: View next topic |
| Author |
Message |
neuron
Advocate
Joined: 28 May 2002
Posts: 2371
|
 Posted: Fri Jul 04, 2008 7:39 am Post subject: poor raid performance |
 |
|
I got 5 sata drives, all doing 80mb/sec according to hdparm, reading raw with dd from /dev/md3 I'm getting 148mb/sec, that seems horrible to me..
The raid was created like this (originally 4 devices, then grown to 5).
| Code: |
mdadm --create --chunk=128 -l 5 -n 4 /dev/sda3 /dev/sdb3 /dev/sdc3 /dev/sdd3
gpg --quiet --decrypt raid-key.gpg | cryptsetup -v --cipher aes-cbc-essiv:sha256 --key-size 256 luksFormat /dev/md3
mkfs.ext3 -b 4096 -E stride=32 /dev/mapper/raid
|
Note that I'm reading raw from /dev/md3, so I'm not testing the encrypted performance.
This is the partition layout:
| Code: |
/dev/sda1 1 609 4891761 fd Linux raid autodetect
/dev/sda2 610 1219 4899825 fd Linux raid autodetect
/dev/sda3 1220 60801 478592415 fd Linux raid autodetect
|
Note that the other partitions are used for backup, and are not currently in use (but are mounted), could I have screwed up the sector alignment on the raid or something funky like that by not using the whole drives?
Any suggestions on how to improve the raw read performance? |
|
| Back to top |
|
 |
massimo
Veteran
Joined: 22 Jun 2003
Posts: 1226
|
| Posted: Fri Jul 04, 2008 7:56 am Post subject: |
|
|
Which RAID controller?
_________________
Hello 911? How are you? |
|
| Back to top |
|
|
neuron
Advocate
Joined: 28 May 2002
Posts: 2371
|
| Posted: Fri Jul 04, 2008 8:29 am Post subject: |
|
|
| massimo wrote: | | Which RAID controller? |
It's linux software raid on a intel p35 chipset, ICH9R controller, but I'm not using the onchip raid function, I'm using mdadm. |
|
| Back to top |
|
|
massimo
Veteran
Joined: 22 Jun 2003
Posts: 1226
|
| Posted: Fri Jul 04, 2008 8:35 am Post subject: |
|
|
I would not expect that performance gain when using software RAID.
_________________
Hello 911? How are you? |
|
| Back to top |
|
|
neuron
Advocate
Joined: 28 May 2002
Posts: 2371
|
| Posted: Fri Jul 04, 2008 8:49 am Post subject: |
|
|
| massimo wrote: | | I would not expect that performance gain when using software RAID. |
It's software raid5 reading, the ICH9R should comunicate directly with NB, which means the performance should be very good based on my limited knowledge.
http://www.issociate.de/board/post/479276/md-raid5,_dm-crypt,_alignment_and_readahead.html this guy is using mdadm and getting 91% of theoretical max read performance. He has a pcie sata2 controller, I got a sata2 controller directly connected to NB, which should be as fast shouldn't it? |
|
| Back to top |
|
|
Mad Merlin
Veteran
Joined: 09 May 2005
Posts: 1155
|
| Posted: Fri Jul 04, 2008 11:41 pm Post subject: |
|
|
| massimo wrote: | | I would not expect that performance gain when using software RAID. |
Well, you might be surprised then. Linux software RAID is typically no slower than real hardware RAID, and almost always faster than fake (motherboard) RAID.
Also, hdparm isn't really a good test of a RAID partition, it tends to give inaccurate results.
_________________
Game! - Where the stick is mightier than the sword! |
|
| Back to top |
|
|
neuron
Advocate
Joined: 28 May 2002
Posts: 2371
|
| Posted: Sat Jul 05, 2008 7:17 am Post subject: |
|
|
| I've been changing settings around, and moving encryption to the lower layer (using dmcrypt, but I was reading raw from the raid in the test I printed), raid+dmcrypt like this I got an unstable 40-50mb/s, now with dmcrypt on the bottom, new chunksize etc, I got 280mb/sec read speed from a file on the encrypted filesystem. And that maxed out one of the cpu's, so I suspect I can go a lot higher (currently on a spare underpowered ups, so the system is constantly in powersave mode). |
|
| Back to top |
|
|
|
Kernel & Hardware
