CentOS - Feb 2014 - Centos 6.5 on USB stick performance / stalls

Hi,

I am running C6.5 64bit on an USB stick connected to a HP DL360G7;
It is usually an ESXi host but eg for firmware updates (not available on 
SPP) I use this local installation.

Problem are the lags and unresponsiveness we are seeing for example when 
running yum update in the installation phase. The whole system stalls 
but there is no io in vmstat.

 From what google tells us, this is a known problem with linux.
But is there anything we can do to mitigate?

steps so far: mount / with ext4: defaults,data=writeback,noatime,nodiratime

Thx
Rainer

On Thu, Feb 27, 2014 at 7:17 AM, Rainer Traut <tr.ml at gmx.de> wrote:
> Hi,
>
> I am running C6.5 64bit on an USB stick connected to a HP DL360G7;
>
You mean flash memory?
(And not a conventional spinning disk drive in an external enclosure.)
Yikes.

> It is usually an ESXi host but eg for firmware updates (not available on
> SPP) I use this local installation.
>
> Problem are the lags and unresponsiveness we are seeing for example when
> running yum update in the installation phase. The whole system stalls
> but there is no io in vmstat.
>
>  From what google tells us, this is a known problem with linux.
> But is there anything we can do to mitigate?
>
> steps so far: mount / with ext4: defaults,data=writeback,noatime,nodiratime
>
Noatime and nodirtime are a step in the right direction to reduce writes on
the flash mem.

If you are indeed on flash memory (and not something reliable like an SSD),
you probably want to ditch journaling.  Journaling is likely killing your
usb stick.  So mount as ext2 rather than ext4.

For flash memory it's a good idea to tune the number of checks until fsck
is forced.
tune2fs -c0 /dev/sdX

There are projects tailored for flash memory (think Voyage Linux) which put
certain items in memory (not on flash) while running.  In Voyage's case it
sets the flash mem partitions to RO and you can only write to those
partitions if you enable RW (I expect it switches to RW on shutdown to
write certain files).


You're probably better off going with an SSD or some other sort of flash
memory meant for all the writes.

>
> Thx
> Rainer
> _______________________________________________
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> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
>


-- 
---~~.~~---
Mike
//  SilverTip257  //

Most USB flash drives have horrid performance, especially for writes and 
doubly especially for random writes. For a live linux distro, I would 
recommend a Sandisk Extreme or anything from Patriot.

Rainer Traut wrote the following on 2/27/2014 6:17 AM:
> Hi,
>
> I am running C6.5 64bit on an USB stick connected to a HP DL360G7;
> It is usually an ESXi host but eg for firmware updates (not available on
> SPP) I use this local installation.
>
> Problem are the lags and unresponsiveness we are seeing for example when
> running yum update in the installation phase. The whole system stalls
> but there is no io in vmstat.
>
>   From what google tells us, this is a known problem with linux.
> But is there anything we can do to mitigate?
>
> steps so far: mount / with ext4: defaults,data=writeback,noatime,nodiratime
>
> Thx
> Rainer
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos

Rainer Traut <tr.ml at ...> writes:
> 
> Hi,
> 
> I am running C6.5 64bit on an USB stick connected to a HP DL360G7;
> It is usually an ESXi host but eg for firmware updates (not available on 
> SPP) I use this local installation.
> 
> Problem are the lags and unresponsiveness we are seeing for example when 
> running yum update in the installation phase. The whole system stalls 
> but there is no io in vmstat.
<SNIP>
> 
I've been running various versions of Fedora from a USB hard drive for
several years and haven't seen anything like what you describe.  I'm
using a
"real" 400GB Western Digital hard drive instead of flash or SSD. 
Given my
experience I'd bet that the lags you're seeing are due to the flash
drive.

Cheers,
Dave