John Drescher wrote:
> On Fri, Sep 26, 2008 at 11:39 AM, Chris Picton <chris AT ecntelecoms DOT com>
> wrote:
>> On Fri, 2008-09-26 at 10:35 -0400, John Drescher wrote:
>>
>>> Here is what I get on a 5 drive software raid5
>>>
>>> # dd if=/dev/zero of=/bigfile bs=1M count=8192
>>> 8192+0 records in
>>> 8192+0 records out
>>> 8589934592 bytes (8.6 GB) copied, 44.8402 s, 192 MB/s
>> I have tried testing directly to the block device, to bypass any
>> filesystem related issues:
>>
>> # cat /proc/mdstat
>> Personalities : [raid6] [raid5] [raid4] [raid0] [raid1]
>> md0 : active raid5 sdg1[5] sdf1[4] sde1[3] sdd1[2] sdc1[1] sdb1[0]
>> 48877120 blocks level 5, 64k chunk, algorithm 2 [6/6] [UUUUUU]
>>
>> # dd if=/dev/zero of=/dev/md0 bs=64k count=65536
>> 65536+0 records in
>> 65536+0 records out
>> 4294967296 bytes (4.3 GB) copied, 57.2713 seconds, 75.0 MB/s
>>
>> # dd if=/dev/zero of=/dev/md0 bs=1M count=4096
>> 4096+0 records in
>> 4096+0 records out
>> 4294967296 bytes (4.3 GB) copied, 113.358 seconds, 37.9 MB/s
>>
>> # cat /sys/block/md0/md/stripe_cache_size
>> 1024
>>
>>
>> Maybe your disks are just a lot faster than mine....
>>
>
> These are Seagate 7200.11 and 7200.10 disks. What kind of controllers
> are you using for your drives? Are any of the drives on just a PCI
> controller and not PCIX or PCIe?
I am using a PCIe megaraid SAS controller, and the drives are 7200 RPM SATA.
I have just tried reconfiguring the drives as a hardware raid 5 array,
and I still only get about 66 MB/sec throughput. I have tried both
ext3, and xfs, with various format and mount options.
Even using md raid 5, with exactly the same xfs mount options as you,
and the same stripe sizes only gives me about 60 MB/sec
I am at a loss as to what you are doing differently to me....
As soon as I switch to RAID 0, I get over 300 MB/sec throughput.
Chris
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