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#1 2011-07-14 17:18:54

lilsirecho
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Registered: 2003-10-24
Posts: 5,000

Upgrading bootable raid0(Success!)

My system was installed to archlinux recently on a raid0 boot setup using two CF cards of 16GB and 533x speed.  These are connected via adapters to sataII ports.

With these devices hdparm -t reports 128mb/s.

Desiring to test the possibilities with mdadm software to add another 16GB CF card.

Be aware that the performance of these cards is obtained anly when used as master devices and they must be UDMA capable.

Thus, to add another CF card requires a command from mdadm besides having another master port at which to connect.  A pcie adapter provided the SataII  master port.

The command in mdadm uses "grow" and requires that  "raid-devices=3" be included to the "add" command.

Thus, the full command is ....mdadm /dev/md0 --grow --raid-devices=3 --add /dev/sdxx.

The ID for my raid may differ for your install.  My install of arch used partitions on the devices, sda1 was the boot device,sda2 was raid,sdb1 was swap,sdb2 raid and the new device sdc1.  The first partitions of sda and sdb were only 100mb in size.

After entering the command above, mdadm starts the remodeling job by setting the raid to m ode4 and proceeds to modify all devices to reestablish raid0.  This can take a very long time if the devices are large (32GB for example).

After the process is completed( in my case the CF cards stopped activity for a minute or so) the indication on my desktop showed the mdadm process still in the display but inactive.  Thus I had to use..... control ^c... to terminate the procedure.

I then checked.../etc/proc/mdstat... and found the raid0 defined with the three CF drives.EDIT

Upon reboot I had to use fallback to enable booting to xfce4 desktop.  Boot is accomplished via sda1 partition which was set-up in initial partitioned raid0.  Thus the sataport for sda1 is selected as first boot device.  I will investigate why the normal boot fails at a later time.

The performance data for this arrangement indicate a successful increase in capacity to 42GB from the ~28GB originally obtained.  Each drive responds with ~65MB/s in hdparm and the resultant /dev/md0 read speed in hdparm was 186MB./s.  This was 128MB/s in the two-device setup.

I do not at present have another CF card to investigate a four-device raid0.

This successful upgrade illustrates one way to increase the capacity and speed of an existing raid0(or any other raid(x)) using --grow.  This is done automatically with mdadm and no re-install is necessary.

I look forward to another escapade with raid0 to search out the unknowns in a four device raid0.  I have an adapter but no CF card.

Performance in archlinux with this raid arrangement seems to be faster...subjective conclusion.

Last edited by lilsirecho (2011-07-14 17:34:03)


Prediction...This year will be a very odd year!
Hard work does not kill people but why risk it: Charlie Mccarthy
A man is not complete until he is married..then..he is finished.
When ALL is lost, what can be found? Even bytes get lonely for a little bit!     X-ray confirms Iam spineless!

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#2 2011-07-15 16:13:51

lilsirecho
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Registered: 2003-10-24
Posts: 5,000

Re: Upgrading bootable raid0(Success!)

Solved the problem with normal boot(not fallback) by running mkinitcpio -p kernel26 in Fallback boot-up.


Prediction...This year will be a very odd year!
Hard work does not kill people but why risk it: Charlie Mccarthy
A man is not complete until he is married..then..he is finished.
When ALL is lost, what can be found? Even bytes get lonely for a little bit!     X-ray confirms Iam spineless!

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#3 2011-07-19 02:40:28

lilsirecho
Veteran
Registered: 2003-10-24
Posts: 5,000

Re: Upgrading bootable raid0(Success!)

Loaded archlinux 64 bit raid0 to four bootable  CF cards today and have 247MB/s read in hdparm.


Prediction...This year will be a very odd year!
Hard work does not kill people but why risk it: Charlie Mccarthy
A man is not complete until he is married..then..he is finished.
When ALL is lost, what can be found? Even bytes get lonely for a little bit!     X-ray confirms Iam spineless!

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#4 2011-07-20 09:44:36

lilsirecho
Veteran
Registered: 2003-10-24
Posts: 5,000

Re: Upgrading bootable raid0(Success!)

Now have 5 devices in arch raid0 boot with 79GB capacity and read speed 306 megabytes per second(Hdparm).


Prediction...This year will be a very odd year!
Hard work does not kill people but why risk it: Charlie Mccarthy
A man is not complete until he is married..then..he is finished.
When ALL is lost, what can be found? Even bytes get lonely for a little bit!     X-ray confirms Iam spineless!

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