question Multiple servers booting from SAS

[cheche]

Hi

I am currently thinking about new server room and after some reading about sas I have a simple question. My idea is to connect few servers to a sas controlled disk array, servers don't have drives only sas hba and boot from logical drives on array, I want to use raid5 for data security.

So my simple question:Is this possible?

Please be gentle.

 

[Bozo]

Sounds like you should investigate virtualization. This would allow multiple operating systems to all run at the same time on the same hardware.

SAS is a SCSI hard drive connected with a serial cable rather than the traditional parrallel cable. It has no bearing on what you want to do. You could SATA drives as well.

 

[cheche]

Nothing virtual, I want hardware servers connect to logical drives on disk array and to boot from those drives.

 

[Stereodude]

You need to make / buy a SAN that uses FiberChannel (FC) and then put FC cards in the servers. All your data is stored on the SAN and uses FC to talk to the external servers. The FC cards in the servers are treated like a disk controller by BIOS / OS.

You could also use iSCSI. It's lower performance, but cheaper.

 

[cheche]

OK, that in basic is the same idea, but can it be done using sas hba cards and sas controlled array?

 

[Mercutio]

SAS doesn't work like that. Fiber Channel does.

 

[ddrueding]

Also even with FC and a SAN, you will need to partition chunks of your array for each computer to boot from. They can't all boot from the same partition.

 

[BingBangBop]

If multiple machines are sharing the same HD's then you have to be VERY careful about the machines caches for there is no cache coherence mechanism between the machines. If any one of the machines writes anything to one of the drives that is cached on another machine you are very likely to corrupt data and/or the file system itself. Keeping each machine to its own partition is a good start.

 

[cheche]

SAS doesn't work like that. Fiber Channel does.

So there's a no. Where I got wrong in this idea?
Is there any way to do something like this using sas?

 

[Howell]

So there's a no. Where I got wrong in this idea?
Is there any way to do something like this using sas?

Fiber channel or iSCSI.

 

[blakerwry]

Basically, SAS is a disk to host interface. It does not have provisions for multiple hosts talking to a single disk.

You might be able to use a single box to house your disks for use by multiple external servers, but that single box would simply be a set of separate physical backplanes and disks - nothing but the power supply would be shared. This solution would offer little beyond using directly connected disks, and as such is probably not recommended.

As others have stated, network aware storage protocols such as iSCSI or FC include a level of abstraction that would allow multiple hosts to access the disks stored in a single machine. It should be noted that iSCSI is an intermediary layer, the underlying disks could be a RAID array, or individual SAS, SATA, SCSI, IDE, or even floppy disks.

 

[cheche]

So something like this 'LSI SAS2108 ROC' or 'Areca 1880 series' with raid controllers wont work?

 

[Mercutio]

So something like this 'LSI SAS2108 ROC' or 'Areca 1880 series' with raid controllers wont work?

SAS does not work that way.