RAID 1 Question

[Moehang]

I creating a file server for a client, I want to set up RAID 1. However, I'd like HD0 (aprox. 2 40-80 GB drives) for the OS. I'd like to set up another HD, HD1 (2 1TB drives for file storage) seperate of the first RAID 1. The files that need to be stored will be large graphic files. This will be my first SCSI - RAID configuration I have ever done, so please forgive my ignorance.

My question is, do I need 2 SCSI controllers to accomplist this? Or can I set up 2 RAID 1 Mirror arrays on 1 SCSI card.

My plan is to back up the HD0 and HD1 (1 TB drive) to off premise location using the Internet via VPN routers.

Any additional information or advice is welcome. Thank you.

[Maverick223]

Sorry for the slow response, I don't believe many folks here know much about SCSI RAID. I have a little basic knowledge because I have been investigating using a SCSI RAID controller for a similar application; I would like to use RAID 5 for the primary 3 HDDs and RAID 1 for the secondary storage HDDs using SATA. From what I have found you may do this if you get the right RAID card, but make sure to check the manufacturer first. Best of luck...Mav.

[DimaYasny]

I creating a file server for a client, I want to set up RAID 1. However, I'd like HD0 (aprox. 2 40-80 GB drives) for the OS.

what exactly are you going to use for the OS? 2x 80Gb drives in Raid1, or did I not get you correctly?

I'd like to set up another HD, HD1 (2 1TB drives for file storage) seperate of the first RAID 1. The files that need to be stored will be large graphic files. This will be my first SCSI - RAID configuration I have ever done, so please forgive my ignorance.

for large files, raid1 is a bit too slow. you will be better off with a few drives in raid5 or raid6 (start of with at least 5 drives to see performance increase), and for large files you need to use a large buffer size, adaptive read ahead and writeback policies.

My question is, do I need 2 SCSI controllers to accomplist this? Or can I set up 2 RAID 1 Mirror arrays on 1 SCSI card.

if you have one SCSI controller that you can connect all the drives to, it will be enough.

[DimaYasny]

Sorry for the slow response, I don't believe many folks here know much about SCSI RAID. I have a little basic knowledge because I have been investigating using a SCSI RAID controller for a similar application; I would like to use RAID 5 for the primary 3 HDDs and RAID 1 for the secondary storage HDDs using SATA. From what I have found you may do this if you get the right RAID card, but make sure to check the manufacturer first. Best of luck...Mav.

the usual practice is to set up raid1 for the OS, and a striped raid (5/5E/6/10/50/etc) for the data

[Moehang]

First off, thank you for your replies.

Yes, I'm planing on using 2x 80GB HDD in RAID1 for the OS. Then 2x 1TB HDD in RAID1 for file storage. There will not my clients accessing the file server at any one time (2 workstations either retrieving or saving files at any giving time, although probably not at the same time) Do you still think I should use RAID 5 or 6 for the file storage? I don't think the client wants to spend the money for all those HDDs.

BTW, I'm thinking purchasing a Motherboard that supports SATA RAID instead of buying a SCSI card. (4x SATA)

[DimaYasny]

the onboard controllers are what we call fakeraid. they are basically almost the same as software based raid, only working through a driver. that makes the raid config not transparent to the OS.

a real raid controller will have it's own cpu, a battery and a memory dimm, and all the parity computation will be performed on the card, not by the main CPU of the system

[Maverick223]

the usual practice is to set up raid1 for the OS, and a striped raid (5/5E/6/10/50/etc) for the data

I think you may have misunderstood me when I said primary, I plan on using it for all programs and data that requires speed. Again thanks Dima for the help in my thread. Do you really think that RAID 5 needs 5+ drives to be appreciably faster (planned on 3)?

Additionally I have to agree with Dima about the RAID controller, I don't believe mobos typically support more than one array (unless it is a server mobo) and they tend to be a little inefficient (slower). However you may be better served by a good SATA RAID card, with onboard RAM to increase the speed.

[DimaYasny]

1. yes, you need many drives, so I would go for several smaller drives instead of 3 large ones. also the raid policy set in the controller is important for performance
2. mobo controllers support several raid drives, but they are not really raid controllers in the full meaning of the word. you might as well use software raid instead (especially under linux - it is much better)

in striped raid configs you need several drives to increase performance, but make sure you don't have too many. i.e. in raid5 6 drives are fast, 8 drives are optimal, and 10 drives are a bit of a slowdown, so you need to go for raid 50 instead (what you would usually get in large SAN environments)