iSCSI continues - The differences between iSCSI (IP SAN) with NAS (File Server)
iSCSI vendors provides better price performance, good security(CHAP authentication, IP SEC encryption), and yet is closing in on performance with the big (Fiber Channel) boys (EMC, HP, HDS, IBM, and more).
iSCSI is the technology to look at. It will give you the ability to do SAN (Storage Area Network) cheaply. Actually today I'd like to backtrack a little bit today. I've jumped ahead to write about iSCSI without saying much about what's out there in the world of storage.
There are three storage topologies in the world:
1. Direct Attached Storage Device (DASD)
2. Network Attached Storage (NAS)
3. Storage Area Network (SAN)
DASD topology is not limited to only internal hard disk drives, it also includes SCSI storage. The external storage that only connects to one server via SCSI cable. SCSI cable is big fat cable, the SCSI cable diameter is about the same with parallel cable (old printer cable). Since DAS or DASD is attached to one server only. That means DAS will only serve one server. If you only have a small number of servers, you will be fine with this topology.
Another example, ABC Corporation has 100+ servers. They have to monitor the free space on every server. If they run out of space, that server will crash, ABC system administrator will spend hours on getting that server back. Utilization is the key for using DAS - imagine this, they have one server that's using up 95% (utilization) of the disk space, the other server is using only 35%. They can not just swap hard drive between the two servers. They'll need to go to ABC finance to get the budget approved, then buy more storage for server with 95% utilization. And they can not do anything to the 35% Util server either.
In DAS environment, you'll find an average of 30-40% of storage (hard drive space) utilization. This means you can save big if you move all your storage together, then share the space.
NAS or File server is next. Any PC (windows, linux, etc..) or server today can serve as a file server. The ability to share files across PCs/servers - file-sharing - is the trademark of a file server. This gives the ability to utilize some space among machines. However, even though now ABC corporation can share some space from the previous 35% utilization server to others. But file server only provides file-based service. E-mail application, database application, and some block-based applications can not run on space provided by a file server.
In addition, managing 100 servers that provide file-server service is a nightmare. It's one big spaghetti all together. That's why we have to move to Storage Area Network (SAN).
SAN is an old idea. Moving all the storage together, then share the storage among servers. 95% util server can request more space online (without stopping application in some cases). 35% utilization server can be taken offline while ABC system administrator move it to a suitable size. Increase 35% util server (35GB usage on 100GB space) to be 70% util server (35GB on 50GB space). And take 50GB from 35% util server to give to 95% util server.
iSCSI and Fiber-Channel are SAN technologies. However since most people know file server (or NAS) that it also works with IP. Some might confuse the relationship between iSCSI and NAS.
NAS provides file-level service (copy, remove, delete, edit). So user can view, edit, delete a file on another machine. Whereas iSCSI provides block-level service, that server will see iSCSI service as a SCSI drive. If you open File Manager on the server, iSCSI service will appear as a drive. So user can put any files into that drive, but user from another machine will not be able to see that drive. Confusing?
Server will treat iSCSI service (space/volume) as a drive. SAN provides high-speed access to its data that would normally provide data reliability through RAID.
Tomorrow, we'll talk about the buzz words. ILM, etc.
iSCSI is the technology to look at. It will give you the ability to do SAN (Storage Area Network) cheaply. Actually today I'd like to backtrack a little bit today. I've jumped ahead to write about iSCSI without saying much about what's out there in the world of storage.
There are three storage topologies in the world:
1. Direct Attached Storage Device (DASD)
2. Network Attached Storage (NAS)
3. Storage Area Network (SAN)
DASD topology is not limited to only internal hard disk drives, it also includes SCSI storage. The external storage that only connects to one server via SCSI cable. SCSI cable is big fat cable, the SCSI cable diameter is about the same with parallel cable (old printer cable). Since DAS or DASD is attached to one server only. That means DAS will only serve one server. If you only have a small number of servers, you will be fine with this topology.
Another example, ABC Corporation has 100+ servers. They have to monitor the free space on every server. If they run out of space, that server will crash, ABC system administrator will spend hours on getting that server back. Utilization is the key for using DAS - imagine this, they have one server that's using up 95% (utilization) of the disk space, the other server is using only 35%. They can not just swap hard drive between the two servers. They'll need to go to ABC finance to get the budget approved, then buy more storage for server with 95% utilization. And they can not do anything to the 35% Util server either.
In DAS environment, you'll find an average of 30-40% of storage (hard drive space) utilization. This means you can save big if you move all your storage together, then share the space.
NAS or File server is next. Any PC (windows, linux, etc..) or server today can serve as a file server. The ability to share files across PCs/servers - file-sharing - is the trademark of a file server. This gives the ability to utilize some space among machines. However, even though now ABC corporation can share some space from the previous 35% utilization server to others. But file server only provides file-based service. E-mail application, database application, and some block-based applications can not run on space provided by a file server.
In addition, managing 100 servers that provide file-server service is a nightmare. It's one big spaghetti all together. That's why we have to move to Storage Area Network (SAN).
SAN is an old idea. Moving all the storage together, then share the storage among servers. 95% util server can request more space online (without stopping application in some cases). 35% utilization server can be taken offline while ABC system administrator move it to a suitable size. Increase 35% util server (35GB usage on 100GB space) to be 70% util server (35GB on 50GB space). And take 50GB from 35% util server to give to 95% util server.
iSCSI and Fiber-Channel are SAN technologies. However since most people know file server (or NAS) that it also works with IP. Some might confuse the relationship between iSCSI and NAS.
NAS provides file-level service (copy, remove, delete, edit). So user can view, edit, delete a file on another machine. Whereas iSCSI provides block-level service, that server will see iSCSI service as a SCSI drive. If you open File Manager on the server, iSCSI service will appear as a drive. So user can put any files into that drive, but user from another machine will not be able to see that drive. Confusing?
Server will treat iSCSI service (space/volume) as a drive. SAN provides high-speed access to its data that would normally provide data reliability through RAID.
Tomorrow, we'll talk about the buzz words. ILM, etc.
posted by Peter Srivaree-Ratana at
4:50 PM
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