Re: Incredibly poor performance of mdraid-1 with 2 SSD Samsung 840 PRO

[Adam Goryachev <mailinglists@websitemanagers.com.au>]

On 24/04/13 18:26, Andrei Banu wrote:
> Hello,
>
> I am sorry for the irrelevant feedback. Where I misunderstood your
> request, I filled in the blanks (poorly).
>
> 1. SWAP
> root [~]# blkid | grep cef1d19d-2578-43db-9ffc-b6b70e227bfa
> /dev/md1: UUID="cef1d19d-2578-43db-9ffc-b6b70e227bfa" TYPE="swap"
>
> So yes, swap is on md1. This *md1 has a size of 2GB*. Isn't this way
> too low for a system with 16GB of memory?
>
Provide the output of "free", if there is RAM available, then it isn't
too small (that is my personal opinion, but at least it won't affect
performance/operations until you are using most of that swap space).

>
> 3. root [~]# fdisk -lu /dev/sd*
>
My mistake, I should have said:
fdisk -lu /dev/sd?

In any case, all of the relevant information was included, so no harm done.
> Disk /dev/sda: 512.1 GB, 512110190592 bytes
> 255 heads, 63 sectors/track, 62260 cylinders, total 1000215216 sectors
> Units = sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disk identifier: 0x00026d59
>
>    Device Boot      Start         End      Blocks   Id  System
> /dev/sda1            2048     4196351     2097152   fd  Linux raid
> autodetect
> Partition 1 does not end on cylinder boundary.
> /dev/sda2   *     4196352     4605951      204800   fd  Linux raid
> autodetect
> Partition 2 does not end on cylinder boundary.
> /dev/sda3         4605952   814106623   404750336   fd  Linux raid
> autodetect
>
> Disk /dev/sdb: 512.1 GB, 512110190592 bytes
> 255 heads, 63 sectors/track, 62260 cylinders, total 1000215216 sectors
> Units = sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disk identifier: 0x0003dede
>
>    Device Boot      Start         End      Blocks   Id  System
> /dev/sdb1            2048     4196351     2097152   fd  Linux raid
> autodetect
> Partition 1 does not end on cylinder boundary.
> /dev/sdb2   *     4196352     4605951      204800   fd  Linux raid
> autodetect
> Partition 2 does not end on cylinder boundary.
> /dev/sdb3         4605952   814106623   404750336   fd  Linux raid
> autodetect
>
I'm assuming from this you have three md RAID1 arrays where sda1/sdb1
are a pair, sda2/sdb2 are a pair and sda3/sdb3 are a pair?

Can you describe what is on each of these arrays?
Output of
cat /proc/mdstat
df
pvs
lvs

Might be helpful....

Regards,
Adam

-- 
Adam Goryachev
Website Managers
www.websitemanagers.com.au