Hardware Thread, File Server - RAID in Technical; I have a HP ProLiant ML110 G4 and G5, I want to use one of them, probably the G4 as ...
4th October 2011, 07:34 PM #1
File Server - RAID
I have a HP ProLiant ML110 G4 and G5, I want to use one of them, probably the G4 as a file server, I am looking to get some 2TB drives and get them raided, I want as much resilience as I can if a disk dies, so doing my reading am I better with a RAID 5 and with this I understand I will not loose to much space due the the raid. I understand I need 3 disks as a minimum and 1 drive will not be used?
I am looking to do this with Server 2003 and will need to invest in a decent raid card to allow this to happen, can someone advise as I am a little out of my depth on this topic!
BTW - this is for home only.
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4th October 2011, 10:25 PM #2
RAID 5 is good, read speed is not amazing compared to some configurations but should be fine for most needs. RAID 6 adds another spare, but needs 4 disks and two are 'lost'.
If you use 3 x 2TB drives, you will get a 4TB array in RAID 5.
Server 2003 is a bit ancient now - do you need to use it?
4th October 2011, 10:44 PM #3
What do you recommend other than RAID 5? It is only for home but want to do it right but don't have a big pot of money, just want to make sure the data is accessible and is protected to some point. Need to invest in a backup solution but don't have the cash for that at the moment.
The reason I am using 2003 is that is all I have, would love to upgrade to a 2008 box but funds will not allow it, plus I already have my domain setup here at home I use.
4th October 2011, 10:59 PM #4
By all means, go for RAID 5. I use it when possible, and when not RAID 1 has served me well - the problem being if RAID 1 has a drive failure it goes offline, where RAID 5 can continue working. I have a few servers running RAID 5 currently, our virtual host uses it, as does our main file server (with onboard RAID that has been surprisingly good) and our two remote (RDP) servers.
4th October 2011, 11:04 PM #5
RAID1 - 2 drives, 2TB space available
RAID5 - 3 drives, 4TB space available
Seeing as it's just going to be a file server, running 2003 isn't going to make any difference to running 2008 R2. If you were to explore any further though, Active Directory is much improved in 2008 R2.
If you wanted to, 2003 and 2008 R2 do support software RAID. It's not something I would recommend, but it works and it would cost you nothing. Of course hardware RAID is always going to be better performance wise in a busy environment.
4th October 2011, 11:15 PM #6
RAID5 it is then. Prefer not to RAID1, want it to be a bit more robust than that.
I would love to start using 2008 more just not got the funds.
I think I have setup a raid before using 2003 sometime ago but would prefer to use a hardware one, any recommendations for a card I can use?
4th October 2011, 11:45 PM #7
As drive sizes get bigger there is an ever increasing risk that array rebuilds will fail if a drive encounters an unrecoverable read error. To minimise the risk in RAID 5, use more drives that have a smaller capacity rather than a few big drives. If you want RAID 1 then the controller will be cheaper, and you could use multiple discs to keep multiple mirrors if it's a critical system (and contrary to what is written above it doesn't go offline when a drive fails) so I would say that it's more robust than RAID 5 but RAID 5 is more flexible as the controller should allow you to grow it with additional disks. If you just want reliability and aren't worried about speed or expandability then RAID 1 is safer.
4 x 1TB drives in RAID 1 gives you 1TB of storage that can take 3 drive failures.
5th October 2011, 12:03 AM #8
Just installed 6 new servers and they have LSI MegaRAID SAS 9240-8i controller cards for Raid 5.
Spec'd the servers after a detailed discussion with the sellers server designers who took on board our needs and budget.
Servers run Windows server 2008 32bit for curriculum and 2008R2 64bit for Admin, 4gb Ram curriculum and 6gb for admin, each server has 1.5tb of storage set up Raid 5 giving us 1TB of usable storage.
Tandberg 320GB SATA RDX drive for local backup.
Servers run great cost about £2000 for each server.
I think the raid cards cost about £230-250 at the time.
hope this helps.
5th October 2011, 12:34 AM #9
Some drives are better than others...
Originally Posted by morganw
Hitachi Deskstar 7K3000 - 1.5TB, 2TB, 3TB
1 sector in every 11.3686838 terabytes (10^14 bits) will have a non-recoverable read error
Samsung SpinPoint F4 EG - 1.5TB, 2TB // Seagate Constellation ES.2 - 3TB
1 sector in every 113.686838 terabytes (10^15 bits) will have a non-recoverable read error
Seagate Cheetah 15K.7 - 600GB // Seagate Savvio 10K.5 - 900GB
Less than 1 sector in every 1.11022302 petabytes (10^16 bits) will have a non-recoverable read error
5th October 2011, 12:43 AM #10
Thanks for the replies, will look at something in the next few weeks hopefully.
5th October 2011, 09:30 AM #11
If this was a larger server I'd say go for RAID 6 - as @morganw points out, the larger drives get the more chance you have of getting a read error while rebuilding an array, and with RAID 6 you at least have another parity disk to fall back on. To be honest, once drives start getting really large then RAID 6 probably isn't going to be quite enough, either, and we'd better start looking at other alternatives - just adding more parity disks probably isn't the best solution, as your RAID array will spend half its life in degraded mode rebuilding after disk failures.
Originally Posted by MatthewL
For a home server, however, RAID 5 should be fine - I have pretty much exactly the kind of setup at home that you're describing, with a Windows Server 2003 server running on a server with a RAID array for storage. My Windows Server 2003 server is a virtual machine, and the RAID array is implemented with Linux software RAID - no need to buy a RAID card for a simple home system. Software RAID's performance can be perfectly good (Qnap NAS devices use Linux software RAID) and any Linux recovery boot CD can generally assemble and read a software RAID array, even if it's been taken apart and plugged into a different motherboard or has elements missing - hardware RAID controllers often get confused if any disk changes.
5th October 2011, 01:38 PM #12
- Rep Power
First, a caution: RAID is not a substitute for backups. It's an availability mechanism, not a disaster-recovery option. Multiple failures can and do occur at times, as our Windows administration team has found out. And more importantly, RAID does nothing to protect against inadvertant overwrite or erasure.
As RAID does reduce the chance of catastrophic storage failure, it can be used to somewhat offset risk of a reduced frequency of backups, but it does not take the place of them. Put another way: With RAID 1 mirrors on my home server, I may be satified with only a weekly backup instead of a daily, since the chance of multiple disk failures is lower -- but it's still there.
RAID 1 is mirroring, with or without a hotspare. The minimum is 2 disks, maximum of 3 if you can afford it. Performance is very high, since the same data is written to both disks and no calculations are necessary. But the effective total storage capacity is one half the total physical storage, or even one third if you use a hot spare. So it's more expensive. I use it (in my day job -- IT Architect) when performance is extremely important, when I only have 2 disks, or when I only have 2 or 3 I/O channels to use. Without a hotspare, when a disk fails, you stay in operation running on the remaining "mirror half," although you have lost all redundancy. Generally, you can hot-swap in a replacement drive, and the array starts chugging, reading from the good" disk and copying blocks to the new disk.. With a hotspare, this happens automatically to return the array to a state of full redundancy as quickly as possible.
RAID 5 requires at least 3 disks. It breaks up the data "stripe" into 2 or more chunks (or "blocks"), and writes one block to each disk. The remaining disk gets a parity block, calculated from the data in the other blocks in the stripe. Each stripe uses the "next" disk in line for parity, so that the parity is spread over all the disks.
Upside of RAID 5 is less "wasted" space -- only 1 disk's worth of space is used for parity overall, so an 8-disk set (sometimes called a "seven plus parity" or "7+P") only "wastes" 1/8th of the space. Though I'd usually set that up with a hotspare, as 6+P+HS.
Downside of RAID 5 is calculation overhead. First, if you are writing a ton of data, say a transactional database, every stripe requires a new parity calculation. For most users, this is not a big deal, which is why RAID 5 is a sweet deal most of the time if you have enough resources to support it.
When a disk fails in RAID 5, the system recreates the "missing" data for the stripe by calculating from the blocks on the remaining disks. this is called "degraded" mode, and you WILL notice the performance hit then. And when hotspare or replacement disk becomes available, the system begins to read EVERY block of EVERY stripe to recalculate the data to write to the new disk, called "rebuilding" the RAID set.
RAID 5's can only tolerate 1 failed disk at a time. As disks get larger, the time needed to rebuild gets larger, so the risk of a second failure gets larger too. RAID 6 "wastes" more spare by storing the parity block for each stripe on two different disks. You can lose a second drive before the first one completes a rebuild, and still stay in business. We use RAID 6 for arrays built on disks larger than 750GB.
BUT IT'S STILL NOT A SUBSTITUTE FOR BACKUPS.
Hope this helps.
5th October 2011, 05:12 PM #13
Raid 5 is common place and used in most of the schools Iíve worked at but you need to be careful!
If you have 5 disks and one fails your server should carry on running ok (without redundancy) on the remaining four (Iíve been in this situation several times) but from experience if an array with 3 disks fails your server will keel over until the faulty drive is replaced and the array is rebuilt from the remaining two drives.
Compare the cost of a few extra drives against what it will cost you if the server is down for a few days while you wait for replacement parts / the array to rebuild.
If you can then use 5 drives for the array and have a 6th as a hot swap so it starts rebuilding as soon as a drive fails reducing the chance of a second failure and waving bye to all of your data.
Raid 5 means the difference between having a server that is down or one that stays online when a drive fails (although you get a performance hit when a drive fails) but itís not a replacement for a backup. I donít have any experience with Raid 6 as I havenít come across it yet in Schools. I imagine the controllers are going to be more expensive and you will get slightly reduced capacity but you do get greater redundancy.
5th October 2011, 05:35 PM #14
This is for home use only.
I am aware it does not replace backups, I just need something that is reliable. I am not good at backing up my data the 500Gb or so I have, been burnt by that once before. Just need something better than using loads of USB drives, want it in one easy accessible place.
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