FAQ Search Today's Posts Mark Forums Read
» Video Reviews

» Linux Archive

Linux-archive is a website aiming to archive linux email lists and to make them easily accessible for linux users/developers.


» Sponsor

» Partners

» Sponsor

Go Back   Linux Archive > Gentoo > Gentoo User

 
 
LinkBack Thread Tools
 
Old 03-16-2010, 07:46 PM
Steve
 
Default Strategy for using SAN/NAS for storage with Gentoo...

On 16/03/2010 19:57, Stroller wrote:
> How does your system boot if your RAID1 system volume fails? The one
> you have grub on? I think you mentioned a flash drive, which I've seen
> mentioned before. This seems sound, but just to point out that's
> another, different, single point of failure.
Well, at the moment, I don't have a RAID system... A flash drive (USB
key) seems a reasonable strategy - I could even have two containing
identical data - so, if the first were to fail then the second would
kick in - if not automatically - then after the duff flash-drive is
removed. A neat side effect of this would be to eliminate a moving part
on the server - making it quieter... and the drives themselves can be
located at two physically remote places on my LAN.

>>> by one client at a time), the simplest solution is to completely avoid
>>> having a FS on the storage server side -- just export the raw block
>>> device via iSCSI, and do everything on the client.
>> ...
>> Snap-shots, of course, are only really valuable for non-archive data...
>> so, in future, I could add a ZFS volume using the same iSCSI strategy.
> If you do not need data sharing (i.e. if your volumes are only mounted
Yes - I don't think I'd need sharing. It strikes me that it should be
possible to have a 'live' backup server which just reads until
fail-over... with a different /var/* - of course.

> I have wondered if it might be possible to create a large file (`dd
> if=/dev/zero of=/path/to/large/file` constrain at a size of 20gig or
> 100gig or whatever) and treat it as a loopback device for stuff like
> this. It's not true snapshotting (in the ZFS / BTFS sense), but you
> can unmount it and make a copy quite quickly.
You could, but the advantage of ZFS is the efficiency of snap-shots.
With your strategy I'd need to process all of the large file every time
I want to make a snapshot... which, even for a mere 100gig, won't be quick.
 
Old 03-16-2010, 08:26 PM
Neil Bothwick
 
Default Strategy for using SAN/NAS for storage with Gentoo...

On Tue, 16 Mar 2010 20:13:29 +0000, Stroller wrote:

> >> How does your system boot if your RAID1 system volume fails?
> >
> > You put GRUB on both disks, then you can boot from either on its
> > own.
>
> Is this reliable? I don't contest it, I'm just asking. It's just this
> was one of my considerations when choosing hardware RAID.

Yes it is, if sda fails unplug it and sdb becomes sda (or hd1 becomes
hd0 in GRUB terms) and the boot continues. Because RAID1 puts the RAID
superblock in a different location from the ordinary one, you can use
either disk from a RAID1 array as a single disk.


--
Neil Bothwick

Minds are like parachutes; they only function when fully open. * Sir
James Dewar
 
Old 03-16-2010, 11:05 PM
Andrea Conti
 
Default Strategy for using SAN/NAS for storage with Gentoo...

> 1. Are there reliability issues surrounding this technology in Gentoo?

My only experience is with a Gentoo-based iSCSI target (ie. "server");
my clients are windows-based. The system is a low-end Core 2 duo running
the latest stable kernel and Iscsi Enterprise Target; I have been
running this setup non-stop for a couple of years and it has proven
quite stable.

iSCSI is designed with a dedicated, reliable network in mind, and in my
experience it is quite sensitive to network connectivity issues. It is
best used over gigabit ethernet; fast ethernet is ok, too, if you don't
care about performace. Avoid WiFi if you value your data (and your
mental health)

> 2. Are there any howtos about putting as much of the file-system as
> possible onto an iSCSI device.

Google "root over iscsi". For example:

http://wpkg.org/Diskless_/_remote_boot_with_Open-iSCSI

I have _not_ tried it. It is an interesting concept, but I think that
the OS is better left on a local disk -- the performance penalty is way
too great, especially with the king of budget-oriented storage backend
you are considering.

> 3. What's the best (most lightweight) way to expose the disk as a
> block device. I don't want to manage three fully-fledged Linux boxes.

The only software you need is an iSCSI initiator: a minimal Gentoo
install running sys-block/iscsitarget is enough.

IET allows you to export any kind of raw block device (a disk, a
partition, a RAID volume,...) or even a file on a local filesystem.

Or perhaps you can look into FreeNAS (http://freenas.org), which is less
flexible than a full-fledged OS install but might be enough in your case.

> Can (cheap) NAS devices be used to export iSCSI to Gentoo?

If the NAS device can "speak" iSCSI, well, yes.

> 4. What would be the strategy to 'secure' this iSCSI device... it would
> be a disaster if my WiFi were cracked and my data corrupted from a
> non-authorised host.

iSCSI connections are authenticated with a challenge-response mechanism;
in IET you can also restrict access to specific hosts on a per-volume
basis. That should be enough if you are not transferring the data itself
over WiFi, which is a Bad Thing and should not be done.

> Snap-shots, of course, are only really valuable for non-archive data...
> so, in future, I could add a ZFS volume using the same iSCSI strategy.

ZFS allows you to take FS-level snapshots -- with iSCSI that would be on
the client, onto a network-connected volume, and I don't know what kind
of performance implications that has.

If you want to take snapshots on the server, my first thought would be
to do so at the block level using LVM. No idea if it plays well with
IET, though.

andrea
 
Old 03-17-2010, 03:57 AM
Keith Dart
 
Default Strategy for using SAN/NAS for storage with Gentoo...

=== On Mon, 03/15, Steve wrote: ===
> Any hints or tips?

===

I recommend setting up your server hardware on a decent mini-PC with
server grade disks and installing openfiler. The openfiler uses XFS for
local storage and exports NFS and CIFS (and iSCSI if you want that).

http://www.openfiler.com/

It is based on rpath linux and uses a different package management
system than you may be used to. But it's relatively easy to configure
and maintain.


-- Keith Dart

--
-- --------------------
Keith Dart
<keith@dartworks.biz>
=======================
 
Old 03-17-2010, 07:03 AM
Steve
 
Default Strategy for using SAN/NAS for storage with Gentoo...

Keith Dart wrote:

I recommend setting up your server hardware on a decent mini-PC with
server grade disks and installing openfiler. The openfiler uses XFS for
local storage and exports NFS and CIFS (and iSCSI if you want that).


http://www.openfiler.com/

It is based on rpath linux and uses a different package management
system than you may be used to. But it's relatively easy to configure
and maintain.


Both Openfiler and FreeNas look promising from a software perspective.
Conversely, I'm drawing a bit of a blank trying to find suitable
hardware to run that software on. Given that all I need is iSCSI to
SATA and back... for 1 drive at 100Mbps.... everything I can find seems
massive overkill.


I've been toying with the idea of abandoning being able to fire-up a
vmware image to stand in for my server... and shifting to accessing raid
storage over USB. It seems a lot less elegant - but it does eliminate
the need for hardware to run multiple kernels... When I thought 'iscsi'
- I'd hoped that I'd find a cheap external drive that supported it
out-of-the-box for a pittance more than a bare drive. Was I was being
hugely overly optimistic?
 
Old 03-17-2010, 12:01 PM
Iain Buchanan
 
Default Strategy for using SAN/NAS for storage with Gentoo...

On Mon, 2010-03-15 at 09:37 -0500, Harry Putnam wrote:

> There was talk of opensolaris going by the wayside with the Oracle
> takeover of Sun... but Oracle has since announced its intention of
> puttin even more resources into `opensolaris' development than Sun was
> doing.

that will kill it for sure! (ok, maybe not, but you know the mythical
man month...)

--
Iain Buchanan <iaindb at netspace dot net dot au>

Life is like a sewer. What you get out of it depends on what you put into it.
-- Tom Lehrer
 
Old 03-17-2010, 07:44 PM
Florian Philipp
 
Default Strategy for using SAN/NAS for storage with Gentoo...

Am 16.03.2010 22:26, schrieb Neil Bothwick:
> On Tue, 16 Mar 2010 20:13:29 +0000, Stroller wrote:
>
>>>> How does your system boot if your RAID1 system volume fails?
>>>
>>> You put GRUB on both disks, then you can boot from either on its
>>> own.
>>
>> Is this reliable? I don't contest it, I'm just asking. It's just this
>> was one of my considerations when choosing hardware RAID.
>
> Yes it is, if sda fails unplug it and sdb becomes sda (or hd1 becomes
> hd0 in GRUB terms) and the boot continues. Because RAID1 puts the RAID
> superblock in a different location from the ordinary one, you can use
> either disk from a RAID1 array as a single disk.
>
>

Just for clarification: Is it really necessary to unplug the broken disk
for this to work?
If read access fails on sda and the BIOS tries sdb, would this also
work? Isn't grub's hd0 always the disk on which grub resides (e.g. the
disk from which grub managed to boot)?

Thanks in advance!
Florian Philipp
 
Old 03-17-2010, 08:00 PM
Neil Bothwick
 
Default Strategy for using SAN/NAS for storage with Gentoo...

On Wed, 17 Mar 2010 21:44:34 +0100, Florian Philipp wrote:

> Just for clarification: Is it really necessary to unplug the broken disk
> for this to work?
> If read access fails on sda and the BIOS tries sdb, would this also
> work? Isn't grub's hd0 always the disk on which grub resides (e.g. the
> disk from which grub managed to boot)?

I suspect that may be dependent on the nature of the failure. For
example, if /boot is corrupted, the BIOS will still boot from the broken
disk's MBR before failing later.

Most BIOSes now enable you to disable individual SATA ports, so you could
disappear the disk without unplugging it, although I'm not sure why you'd
want to leave a broken disk in the box.


--
Neil Bothwick

This is the day for firm decisions! Or is it?
 
Old 03-18-2010, 03:57 PM
Florian Philipp
 
Default Strategy for using SAN/NAS for storage with Gentoo...

Am 17.03.2010 22:00, schrieb Neil Bothwick:
> On Wed, 17 Mar 2010 21:44:34 +0100, Florian Philipp wrote:
>
>> Just for clarification: Is it really necessary to unplug the broken disk
>> for this to work?
>> If read access fails on sda and the BIOS tries sdb, would this also
>> work? Isn't grub's hd0 always the disk on which grub resides (e.g. the
>> disk from which grub managed to boot)?
>
> I suspect that may be dependent on the nature of the failure. For
> example, if /boot is corrupted, the BIOS will still boot from the broken
> disk's MBR before failing later.
>
> Most BIOSes now enable you to disable individual SATA ports, so you could
> disappear the disk without unplugging it, although I'm not sure why you'd
> want to leave a broken disk in the box.
>
>

Just in case I ever face high demands on uptime. It's good to know
whether I can still (remote) reboot a machine and it will come up
although one of its drives is broken.
 

Thread Tools




All times are GMT. The time now is 11:57 PM.

VBulletin, Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO ©2007, Crawlability, Inc.
Copyright 2007 - 2008, www.linux-archive.org