RAID, an acronym for Redundant Array of Independent Disks (sometimes incorrectly referred to as Redundant Array of Inexpensive Disks), is a technology that provides increased storage functions and reliability through redundancy. -Wikipedia

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98
votes
2answers
12k views

What are the different widely used RAID levels and when should I consider them?

This is a Canonical Question about RAID levels. What are: the RAID levels typically used (including the RAID-Z family)? deployments are they commonly found in? benefits and pitfalls of each? ...
54
votes
13answers
23k views

Why is RAID not a backup?

When someone mentions RAID in a conversation about backups, invariably someone declares that "RAID is not a backup". Sure, for striping, that's true. But whats the difference between redundancy and a ...
42
votes
10answers
6k views

RAID - software vs. hardware

I have always used hardware based raid because it (IMHO) it's on the right level (feel free to dispute this) and that OS failures are more common to me than hardware issues. Thus if the OS fails the ...
26
votes
9answers
5k views

To improve SQL performance, why not just put lots of RAM rather than having faster hard disks?

People keep telling me that in order to improve an SQL server's performance, buy the fastest hard disks possible with RAID 5, etc. So I was thinking, instead of spending all the money for ...
26
votes
14answers
12k views

File Server - Storage configuration: RAID vs LVM vs ZFS something else…?

We are a small company that does video editing, among other things, and need a place to keep backup copies of large media files and make it easy to share them. I've got a box set up with Ubuntu ...
25
votes
6answers
38k views

How to interrupt software raid resync?

I want to interrupt a running resync operation on a debian squeeze software raid. (This is the regular scheduled compare resync. The raid array is still clean in such a case. Do not confuse this with ...
24
votes
5answers
2k views

Do I need to RAID Fusion-io cards?

Can I run reliably with a single Fusion-io card installed in a server, or do I need to deploy two cards in a software RAID setup? Fusion-io isn't very clear (almost misleading) on the topic when ...
24
votes
7answers
39k views

Should I RAID my SSDs?

I have a couple of SATA hard disks RAIDed for safety in my machine, because I'm worried about the drive having some sort of mechanical failure and losing my data. I'm considering switching to an SSD ...
24
votes
7answers
11k views

What are the performance differences between Raid 0,1,5,6,10

I have heard/read different performance stories on the various raid flavors. I am curious what the agreed upon best answer is.
23
votes
1answer
2k views

When using software RAID and LVM on Linux, which IO scheduler and readahead settings are honored?

In the case of multiple layers (physical drives -> md -> dm -> lvm), how do the schedulers, readahead settings, and other disk settings interact? Imagine you have several disks (/dev/sda - /dev/sdd) ...
22
votes
13answers
2k views

High Failure Rate of Large Drives?

I recently deployed a server with 5x 1TB drives (I won't mention their brand, but it was one of the big two). I was initially warned against getting large capacity drives, as a friend advised me that ...
22
votes
6answers
3k views

Scaling databases with cheap SSD hard drives

I hope that many of you are working with high traffic database-driven websites, and chances are that your main scalability issues are in the database. I noticed a couple of things lately: Most large ...
21
votes
4answers
1k views

Do raid controllers syncronize HDD platter rotation?

I'm in the market for a new storage solution. While researching various specs one of my coworkers said that some raid controllers can synchronize HDD rotation to the effect of all drives' sector/block ...
21
votes
3answers
8k views

Should I defrag my RAID volumes?

It seems to me that since RAID volumes are logical (as opposed to physical), the layout that the OS believes they have might not correspond to the actual phsyical layout. So does defrag make sense ...
20
votes
5answers
15k views

How do I differentiate “fake RAID” from real RAID?

The Ubuntu wiki page on FakeRaid says the following: [A] number of hardware products ... claim to be IDE or SATA RAID controllers... Virtually none of these are true hardware RAID ...
20
votes
8answers
3k views

Do RAID controllers commonly have SATA drive brand compatibility issues?

We've struggled with the RAID controller in our database server, a Lenovo ThinkServer RD120. It is a rebranded Adaptec that Lenovo / IBM dubs the ServeRAID 8k. We have patched this ServeRAID 8k up to ...
19
votes
5answers
8k views

What is better LVM on RAID or RAID on LVM?

I currently have LVM on software RAID, but I'd like to ask you what you think it is better solution, maybe some pros and cons? Edit: It is about software raid on lvm or lvm on software raid. I know ...
16
votes
2answers
3k views

RAID-6: better to replace two dead drives at the same time, or one at a time?

We have a 16-drive RAID-6 that has three problem drives. Two are already dead, and the third is giving SMART warnings. (Nevermind how it got in such a bad state.) Obviously we want to replace the ...
16
votes
8answers
1k views

Optimal UNIX File System Partition + Setup Strategy

When partitioning a new system disk(s) for UNIX, what is your prefered strategy for both desktop and/or servers? Please include disk partition layout, file system format(s) and options, mount points, ...
16
votes
5answers
10k views

Possible to get SSD TRIM (discard) working on ext4 + LVM + software RAID in Linux?

We use RAID1+0 with md on Linux (currently 2.6.37) to create an md device, then use LVM to provide volume management on top of the device, and then use ext4 as our filesystem on the LVM volume groups. ...
15
votes
12answers
6k views

Should a backup server use RAID?

I was asked to set up a new backup server using Symantec Backup Exec that stores to hard disk instead of tape, because the backup size is outgrowing tape capacity. I was wondering does it really ...
15
votes
3answers
2k views

Is there a difference between RAID 10 (1+0) and RAID 01 (0+1)? [duplicate]

I've seen both of these listed, both being striped and mirrored across multiple drives, but is the a difference between them that I'm not picking up on?
15
votes
4answers
9k views

Hardware RAID Controller Support for SSD TRIM

Do any hardware RAID controllers available today support TRIM? If not, do any manufacturers have target dates for supporting TRIM? Should I even care about TRIM for SSDs installed in ...
15
votes
2answers
7k views

Can you change the metadata version on an existing array?

So grub requires metadata version 0.90 I'm wondering if I can change my existing arrays to use that instead of the default which is 1.2. That way I don't have to go about a reinstall. If yes, how can ...
15
votes
2answers
2k views

Verify A Partition is Aligned in Linux With RAID and LVM

Does anyone know the steps to verify that a XFS filesystem on top of LVM and md RAID is properly aligned on an array of 4096 Byte aka "Advanced Format" sectored disks? Some references are: ...
14
votes
8answers
2k views

Do snapshots + RAID count as a good on-site backup solution?

The two main reasons I can think of for taking backups seems to be taken care of when I use both snapshots and RAID together with btrfs. (By RAID here, I mean RAID1 or 10) Accidental deletion of ...
13
votes
21answers
4k views

When is RAID worth the trouble?

In our shop we're faithfully using RAID in all our workstations, probably just because that seems to be the way it ought to be done. I'm talking about workstations for scientific simulations, using ...
13
votes
8answers
1k views

RAID configuration for large NAS

I'm thinking of building a 24 1TB disk NAS box, but I'm not sure what the best drive configuration is. I'm looking at using the areca ARC-1280ML-2G controller, and hanging all 24 drives off of it. ...
12
votes
11answers
7k views

Should I run my database off of a RAID 5 configuration?

I've heard that the write performance of RAID 5 can be appalling at times. While I want the redundancy that it provides I don't want to sacrifice my database insert/update times. Is this something I ...
12
votes
7answers
3k views

How many SMART sector reallocations indicate problems?

I have a NAS appliance that is just over a month old. It is configured to email me alerts generated from the hard drives' SMART data. After one day, one of the hard drives reported that a sector had ...
12
votes
6answers
648 views

Bad disks in ancient server

I have a 1998-era Netware 3.12 server that runs everything on our campus: general ledger, purchasing, payroll, student information, grades, you name it. The server has an Adaptec RAID controller with ...
12
votes
9answers
6k views

Is using 2 solid state drives in RAID 0 going to be reliable?

I am thinking of upgrading from a Western Digital 10k RPM hard drive to using two Intel-X25 solid state drives in RAID 0 configuration. I will be using this for hosting the operating system and ...
12
votes
11answers
2k views

Is RAID5 more robust than RAID1

I am about to replace an old hardware RAID5 array with a Linux software RAID1 array. I was talking to a friend and he claimed that RAID5 was more robust than RAID1. His claim was that with RAID5, on ...
12
votes
4answers
15k views

Recommended disk/partition setup for a SQL Server

I'm looking for some advice regarding the best way to set up my disks/partitions for SQL Server. Here are some of my major concerns: How should the SQL files be seperated (data files, logs, temp)? ...
11
votes
4answers
910 views

SQL Server setup check list

What are the things I have to consider when I have to install SQL Server (2005/2008) on a new server? Storage setup TempDB Security What are some common mistakes made in that process?
11
votes
4answers
734 views

Should you still spread a hard drive order over several vendors?

Once upon a time, I was taught to spread drive orders for at least around six disks or so to at least two vendors, three vendors if there are more than 20 disks. Use the same make and model of disk, ...
11
votes
6answers
677 views

How to utilize spare workstation drive space for server storage/backup

So, given the fact that you can only get hard drives of about 160GB now for the cheapest price, I find i have a ton of extra drive space on workstations spread throughout my office. I'd like to ...
10
votes
7answers
620 views

Can a RAID 4 disk setup crash if only 1 hard disk fails? [closed]

I am a web developer. I have not much experience in hardware. For this reason, I use managed servers. This morning, one of the drives in our setup failed. However, the full site went down. I ...
10
votes
7answers
2k views

How do you backup a storage server?

I'm looking at implementing a very large storage server to be used as live NAS for several other servers (all Linux-based). By very large, I mean between 4TB and 20TB usable space (although it's ...
10
votes
6answers
8k views

Is bit rot on hard drives a real problem? What can be done about it?

A friend is talking with me about the problem of bit rot - bits on drives randomly flipping, corrupting data. Incredibly rare, but with enough time it could be a problem, and it's impossible to ...
10
votes
3answers
887 views

Should I avoid putting two SSDs in a RAID1 configuration due to performance degradation?

I have a workstation system that will have two 64GB industrial SSDs, and the plan is to have both disks in a RAID1 configuration for redundancy which is set up in the kickstart. The system will be ...
10
votes
2answers
744 views

Why is my RAID1 read access slower than write access?

I have done some simple performance tests and it seems that reading from my RAID1 is slower than writing: root@dss0:~# for i in 1 2 3; do dd if=/dev/zero of=/dev/sda bs=1048576 count=131072; done ...
10
votes
3answers
8k views

Battery Backed Write Cache

I recently got some U server price quotes and some of them include BBWC: What exactly does it do? Is it just for RAID configurations? If there is a power malfunction, isn't the data loss ...
10
votes
7answers
3k views

Hot spare or extra parity drive in RAID array?

In a different question about configuring a RAID array, the author is building a RAID array with 8 drives. One answer suggests using 7 drives in RAID 5 with one left over as a hot spare. Since RAID 6 ...
10
votes
1answer
6k views

Easy to expand Linux software RAID 5 with XFS. Best practices?

I use my Ubuntu machine as a file server for Windows/Linux/Mac clients using a Samba share. I need it to be easily expandable by just adding more hard drives without having to move any data back and ...
9
votes
12answers
1k views

How to remember RAID levels? [duplicate]

How do you remember(if you really do :-)) all the different levels and what each level does? Can anyone suggest an easy way to remember?
9
votes
13answers
738 views

Should a sys admin backup important data in anyway he can, even if he disagrees with the backup strategy?

Recently, one of the main file servers at our company failed. It was using a 4 disk RAID array, but apparently 3 of the disks died, and all the data on the server has been lost. Speaking to the sys ...
9
votes
9answers
15k views

How many disks is too many in this RAID 5 configuration?

HP 2012i SAN, 7 disks in RAID 5 with 1 hot spare, took several days to expand the volume from 5 to 7 300GB SAS drives. Looking for suggestions about when and how I would determine that having 2 ...
9
votes
7answers
24k views

What is a (raid-controller-) BBU for?

I am wondering what's the purpose of a BBU. My first understanding was, that it enables the cache to write the data to the disc during a power failure. But some specifications say that a BBU can hold ...
9
votes
2answers
6k views

How to upgrade a ZFS RAID-Z array to larger disks on OpenSolaris?

I'm planning on installing OpenSolaris on my home server (right now it has Linux) and I would like to know how to prepare for upgrading the server to have larger hard drives in the future. Now the ...