Hello,

is there any linux driver that makes it possible to use an flash drive like
an USB stick as cache for the disks?


Thank you very much!
AD

On 2007-10-06, Arthur Dent <arthur@dent.net> wrote:
> Hello,
>
> is there any linux driver that makes it possible to use an flash drive like
> an USB stick as cache for the disks?

This is not the healthiest of options for your usb stick (FLASH) which
has a max writes limit.

Perhaps we could help you in some other way if you explained what you wish
to accomplish.

--
Davorin Vlahoviæ. Smetam ljudima od 1982.

Hi Davorin,

>> is there any linux driver that makes it possible to use an flash drive
>> like
>> an USB stick as cache for the disks?
>
> This is not the healthiest of options for your usb stick (FLASH) which
> has a max writes limit.

i know ... but never heard about an usb stick that really crashed because of
too many writes ...
.... and with currently 8 Euro per GB i could buy a new after one or two
years ...


> Perhaps we could help you in some other way if you explained what you wish
> to accomplish.

i'm running an old desktop as small server at home. Apps running are LAMP,
IMAP, Postfix and Samba.
There are 2 disks inside as softraid 1. Works well ...

But 99% of time the server is doing nothing ... expect logging cronjobs to
/var/log/messages and writing some weather-data to the mysql-database ... i
think 1 or 2 GB flash storage could cache all files the server needs over
the day (read and write cache) ...

The disks could go to powersave and start again when data is not in flash or
the write back cache of the flash is full ... saving energy, noise and
lifetime of the disks ...


.... that about my plans ;-)

Installing the linux root partition on usb-stick isn't an option, i think
.... i would become problems to install all apps to a 16 GB SSD (which isn't
a cheap solution ;-)


Thank you for suggestions,
AD

On Sat, 06 Oct 2007 22:57:54 +0200, Arthur Dent wrote:

> Hello,
>
> is there any linux driver that makes it possible to use an flash drive like
> an USB stick as cache for the disks?
>
>
> Thank you very much!
> AD

Besides the aforementioned finite life, it's going to be significantly
slower than a hard disk.

ray wrote:
> On Sat, 06 Oct 2007 22:57:54 +0200, Arthur Dent wrote:
>
>> Hello,
>>
>> is there any linux driver that makes it possible to use an flash drive like
>> an USB stick as cache for the disks?
>>
>>
>> Thank you very much!
>> AD
>
> Besides the aforementioned finite life, it's going to be significantly
> slower than a hard disk.
>

Even Thoms Hardware thought the harddrives with built in flash wasn't anything
else than waste of money and could even be slower than conventional harddrives.

--

//Aho

Arthur Dent wrote:

> But 99% of time the server is doing nothing ... expect logging cronjobs to
> /var/log/messages and writing some weather-data to the mysql-database ... i
> think 1 or 2 GB flash storage could cache all files the server needs over
> the day (read and write cache) ...

You could mount the /var/log/ on an USB, more problematic would be the cron
jobs, as you need to mount all the directories where you have the binaries to
be used.


> The disks could go to powersave and start again when data is not in flash or
> the write back cache of the flash is full ... saving energy, noise and
> lifetime of the disks ...

Once in the time I used powersave on some less used hard drives on my server,
but the spinning up of those hard drives made that things halted up, made that
the server felt extremely slow when it had to access those hard drives, made
me to decide to better to use hard drives with low energy usage, these are
usually quiet too.

Powersave mode is something that shortens the lifespan of the hard drive, the
best life span you get to have those stay slightly hot, according to Google
researches.



--

//Aho

Arthur Dent wrote:

> Hello,
>
> is there any linux driver that makes it possible to use an flash drive
> like an USB stick as cache for the disks?

/Not/ a good idea. Flash memory has a very limited number of writes
available, and would quickly become unusable. It's also /very/ slow
compared to your system memory.

Buy some more memory for your machine, and allocate some RAM disks. You can
use one for swap and another for disk cache, if you want.

C.

Wouldn't using a RAM disk be unsafe because of the possible event of a power
failure?
Can anyone point me in the direction of how to change the disk cache

"Christopher Hunter" <chrisehunter@NOSPAMblueyonder.co.uk> wrote in message
news:kY7Oi.403471$p7.280702@fe2.news.blueyonder.co .uk...
> Arthur Dent wrote:
>
>> Hello,
>>
>> is there any linux driver that makes it possible to use an flash drive
>> like an USB stick as cache for the disks?
>
> /Not/ a good idea. Flash memory has a very limited number of writes
> available, and would quickly become unusable. It's also /very/ slow
> compared to your system memory.
>
> Buy some more memory for your machine, and allocate some RAM disks. You
> can
> use one for swap and another for disk cache, if you want.
>
> C.

Michael Everson wrote:

> Wouldn't using a RAM disk be unsafe because of the possible event of a
> power failure?

Not if you do the sensible thing, and install a UPS. The public supply
around here is pretty flaky at the moment, so I invested in UPSs for my
more critical machines.

C.

Hi Christopher,

>> is there any linux driver that makes it possible to use an flash drive
>> like an USB stick as cache for the disks?
>
> /Not/ a good idea. Flash memory has a very limited number of writes
> available, and would quickly become unusable. It's also /very/ slow
> compared to your system memory.

performance isn't a problem ... 1 GHz PIII and slow IDE drives ...
As I read a good USB2 flash has 40 MBit/s read


> Buy some more memory for your machine, and allocate some RAM disks. You
> can
> use one for swap and another for disk cache, if you want.

I've 1 GB SDRAM inside ... more does the mainboard not support ...

How to configure a disk cache on RAM disk?
Maybe i can set up the flash-cache the same way.


Thank you :-))