Software raid over iSCSI

2008-12-22 Thread Eric
Hello, I'm going to setup a software raid over iSCSI. While I probably should ask my question to the raid people, my guess was someone here might have experience with this. I'm going to use the following topology: There will be 2 storage servers exporting targets. Other physical machines will i

Re: Software raid over iSCSI

2008-12-22 Thread Yuri
like this? http://groups.google.com/group/open-iscsi/browse_thread/thread/4caaf406fe8165ab/f021bae5e175ed59#f021bae5e175ed59 2008/12/22 Eric > > Hello, > > I'm going to setup a software raid over iSCSI. While I probably should > ask my question to the raid people, my guess was someone here migh

Re: Software raid over iSCSI

2008-12-22 Thread Bart Van Assche
On Mon, Dec 22, 2008 at 11:19 AM, Eric wrote: > Apart from the standard optimizations, there's one I haven't been able > to find any information on. It is suggested that initiators, using the > disks (in this case the virtualized machines) should use a head and > cylinder count that is divisable

Re: Software raid over iSCSI

2008-12-22 Thread Eric
Yuri, Assuming the disks used by your raid are targets originating from different servers, then yes. On Dec 22, 11:27 am, Yuri wrote: > like > this?http://groups.google.com/group/open-iscsi/browse_thread/thread/4caaf4... > > 2008/12/22 Eric > > > > > > > > > Hello, > > > I'm going to setup a

Re: Software raid over iSCSI

2008-12-22 Thread Eric
We'd be using "iSCSI Enterprise Target" (iscsitarget.sourceforge.net). Ofcourse, the target implementation to use in this setup is open for discussion. On Dec 22, 12:00 pm, "Bart Van Assche" wrote: > On Mon, Dec 22, 2008 at 11:19 AM, Eric wrote: > > Apart from the standard optimizations, there'

Re: Software raid over iSCSI

2008-12-22 Thread Ulrich Windl
On 22 Dec 2008 at 2:19, Eric wrote: > > Hello, > > I'm going to setup a software raid over iSCSI. While I probably should > ask my question to the raid people, my guess was someone here might > have experience with this. > > I'm going to use the following topology: > > There will be 2 storage

Re: Software raid over iSCSI

2008-12-22 Thread Bart Van Assche
On Mon, Dec 22, 2008 at 1:18 PM, Ulrich Windl wrote: > I think since ZBR (Zone Bit Recording) the number of sectors per cylinder is > variable. thus it makes no sense for any higher-level disk software to try to > deal > with heads or cylinders. Since ATA (about 1990) only the controller on the

Re: Software raid over iSCSI

2008-12-22 Thread Eric
Ulrich, According to what I read, whilst not directly affecting the physical disk, heads and cylinders do matter. It has something to do with the IO scheduler where it causes misalignemnt. It's a long story but it comes down to roughly twice the disk activity than is actually necessary. It seems

Re: Software raid over iSCSI

2008-12-22 Thread Eric
Bart, Thanks for definitive answer and the link to a great thread. I need one more: I have to set the heads and cylinders on the disk partitions of the virtualized servers. Now I assume I also have to set heads and cylinders on the raid partions, exported by the targets. Is this assumption corre

Re: Software raid over iSCSI

2008-12-22 Thread Bart Van Assche
On Mon, Dec 22, 2008 at 2:17 PM, Eric wrote: > > Thanks for definitive answer and the link to a great thread. I need > one more: > > I have to set the heads and cylinders on the disk partitions of the > virtualized servers. Now I assume I also have to set heads and > cylinders on the raid partion

Re: Software raid over iSCSI

2008-12-22 Thread Eric
Bart, My use of the term partitions is terrible abuse ofcourse. I mean the CHS layout ofcourse. I've a semi-production test setup where I will apply these changes and see what happens. The setup is far from ideal because if have some cheap-ass 3com switches which don't support jumbo frames or 80

Re: Software raid over iSCSI

2008-12-22 Thread Ulrich Windl
On 22 Dec 2008 at 5:11, Eric wrote: > Besides that, I don't think I totally agree on your statement. Letting > the IO scheduler taking the actual disk geometry into account, should > give more performance. However, the fdisk default values are probably > standard for disks these days. The disk s