Neil, Can you explain how RAID 10 would work with 4 x 1tb drives?

Should I just get 2 x 2tb drives and mirror?

I probably dont need 4 x 1tb drives to start, maybe even 2 x 2tb. I can't image this growing faster than I can get money to add more equipment, move to Co-Lo, etc.

On Oct 29, 2009, at 10:59 AM, Neil Aggarwal wrote:

If you want speed, use RAID 10.

Neil

-- Neil Aggarwal, (281)846-8957, http://www.JAMMConsulting.com CentOS 5.4 KVM VPS $55/mo, no setup fee, no contract, dedicated 64bit CPU 1GB dedicated RAM, 40GB RAID storage, 500GB/mo premium BW, Zero downtime

...

-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of ML Sent: Thursday, October 29, 2009 12:57 PM To: CentOS mailing list Subject: [CentOS] Infrastructure HELP!

Hi Everyone,

I started a social networking site and I am getting ready to go live next week. I have limited fund as I am not funded yet (although hopefully soon).

I have an extra Mac Pro (I know, how can I possibly call a Mac Pro dual 2.8 quad core with 16gb RAM extra). So Mac Pro quad Core, 16gb RAM, 4 x 1tb RAID level Seagate drives. I was going to load CentOS 5.4 on it, web, mysql etc, etc. This is really the only box I have that would handle the site it it takes off and then I would need to add more hardware and most hosting to RackSpace or something.

My question is about initial setup. The 4 x 1TB drives. How to set this up for I have some protection?

RAID 0+1? (striped + mirrored) I would end up with 2TB useable space.

RAID 5? so what one is a hot spare? 3TB useable space?

What about striping the 4 1TB and mirroring that to a 4 x 1tb External drive enclosure?

I want to be sure the data is protected, but machine resources and money are limited.

Thoughts are appreciated! _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos

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CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos

On Thu, 29 Oct 2009, Neil Aggarwal wrote:

Also, when you move to a hosted solution, I would appreciate your considering my company for it.

Neil

When stuff like this moves out of the sig and into the body of the message as a direct solicitation, and (as it seems to me) a person is camping on the mailing list with fast but not necessarily thoughtful asnwers, they are spamming the list, and stepping over the bounds of proper conduct.

My opinion, and for what it is worth, sent in my personal email, rather than a @centos.org one

May I ask that you not repeat this approach, please?

-- Russ herrold

Would 2 x 1TB enterprise drives be enough mirrored?

Are you going to to software RAID1 or hardware?

I find software RAID1 bogs down for intensive database applications.

NOTE: Host based RAID is the same as software RAID. You will need an actual external RAID card like one from Areca.

Neil

-- Neil Aggarwal, (281)846-8957, http://www.JAMMConsulting.com CentOS 5.4 KVM VPS $55/mo, no setup fee, no contract, dedicated 64bit CPU 1GB dedicated RAM, 40GB RAID storage, 500GB/mo premium BW, Zero downtime

If I can find a cheap enough RAID Card that wil fit the Mac Pro, I would do hardware RAID, but Apple wants $699 for theirs...

$699 is pretty steep, but RAID cards are not cheap. They are worth it for performance though.

If you don't need absolute performance, software RAID will work.

Give with multiple smaller drives instead of two larger ones.

Neil

-- Neil Aggarwal, (281)846-8957, http://www.JAMMConsulting.com CentOS 5.4 KVM VPS $55/mo, no setup fee, no contract, dedicated 64bit CPU 1GB dedicated RAM, 40GB RAID storage, 500GB/mo premium BW, Zero downtime

$700, eesh.  You can get some nice Areca cards for much less than that.

What is the cheapest SATA hardware raid card I can get at newegg.com? Seems like most turn out not to be true hardware raid that I have found and will not run on CentOS 4.8 without a great deal of grief.

Matt

On Thu, 29 Oct 2009, Matt wrote:

What is the cheapest SATA hardware raid card I can get at newegg.com? Seems like most turn out not to be true hardware raid that I have found and will not run on CentOS 4.8 without a great deal of grief.

Not a direct answer to your question, but be careful of SATA drives.

As I understand it SAS drives (Serially Attached SCSI) are designed to handle server duty (multiple processes stepping the head 24/7), whereas SATA drives (Serially attached ATA) are not. SATA drives if used in servers will fail prematurely. They're great/cheap for home use though.

I've also heard that SATA-2 drives are more like SAS or SCSI drives in this respect, as in they're designed for server duty.

I probably heard the above on this very list in the past.

Can someone confirm or deny? Making me look like a fool is ok, I'm used to it. ;-)

On Fri, 2009-10-30 at 09:57 +1300, Clint Dilks wrote:

Curt Mills wrote:

...

On Thu, 29 Oct 2009, Matt wrote:

...

What is the cheapest SATA hardware raid card I can get at newegg.com? Seems like most turn out not to be true hardware raid that I have found and will not run on CentOS 4.8 without a great deal of grief.

Not a direct answer to your question, but be careful of SATA drives.

As I understand it SAS drives (Serially Attached SCSI) are designed to handle server duty (multiple processes stepping the head 24/7), whereas SATA drives (Serially attached ATA) are not. SATA drives if used in servers will fail prematurely. They're great/cheap for home use though.

I've also heard that SATA-2 drives are more like SAS or SCSI drives in this respect, as in they're designed for server duty.

I probably heard the above on this very list in the past.

Can someone confirm or deny? Making me look like a fool is ok, I'm used to it. ;-)

We use SATA in a number of Production Systems. If its server class hardware I haven't seen issues. So I wouldn't treat this as a big concern.

---- there actually are server and consumer grade SATA drives and you should be very careful about what you are buying.

Then there's the thought that any SATA drive runs the risk of data loss in a RAID-5 or RAID-6 setup...

http://www.enterprisestorageforum.com/technology/features/article.php/383963...

Craig

Not a direct answer to your question, but be careful of SATA drives.

Seagate does make enterprise SATA drives.

-- Neil Aggarwal, (281)846-8957, http://www.JAMMConsulting.com CentOS 5.4 KVM VPS $55/mo, no setup fee, no contract, dedicated 64bit CPU 1GB dedicated RAM, 40GB RAID storage, 500GB/mo premium BW, Zero downtime

If you want performance stick with RAID 10. In general the more drives (spindles) the faster the array. The Western Digital RE3 500 GB drives are a good deal. You should be able to get 4 of those in the low $200s. In RAID 10 this would give you better performance than 2 x 1TB in RAID 1.

Ryan

On Thu, Oct 29, 2009 at 2:36 PM, ML mailinglists@mailnewsrss.com wrote:

On Oct 29, 2009, at 11:11 AM, Neil Aggarwal wrote:

...

RAID 10 is striping across mirrored drives.

So, if you have 4 x 1TB drives, think of it as two separate 1 TB volumes.  The system will write half your data to volume A and the other half to volume B.  The data in volume A and B do not overlap.

Now, each volume is composed of a mirrored set of drives. Anything written to volume A is actually stored on two drives. Anything written to volume B is actually stores on the other two drives.

Does this make sense? Let me know if you need any more explanation.

No it makes sense.

I am contemplating if I really need 4 x 1tb in this system. I mean how much space with some photo's, web pages and MySQL take up if there are 5,000 subscribers to start up?

Would 2 x 1TB enterprise drives be enough mirrored?

...

Also, when you move to a hosted solution, I would appreciate your considering my company for it.

Sure, I will be doing a lot of research on that for sure. _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos

Is software RAID 10 decent performance?

depends on the workload.

committed random writes are greatly accelerated by battery backed write caches on real raid controllers. this greatly speeds up things like transactional databases.

if your workload is mostly read, software raid performs quite adequately.

with 4 x raid10, you can be doing 4 different reads at once, or two writes simultaneously, as long as you have plenty of pending IO requests.

Looks like the price has gone up with the economy starting to recover. I paid $68 per WD RE3 500GB drive on Amazon.com back in June.

I would still recommend going with 4 drives in RAID 10 over 2 in RAID 1 or even 3 drives in RAID 5. You will get almost double the performance due to being able to stripe across the drives. RAID 1 is just a mirror so you are only going to see the performance of a single drive.

I have experience with software RAID levels 1 and 5 with mdadm. My file server has a RAID 1 of 2 x 160GB Seagate SATA Drives and a RAID 5 of 3 x 1TB Hitachi SATA drives. For the RAID 1 drives hdparm shows approx 68MB/s for each drive and 68MB/s for the array. With the RAID 5 I am seeing 82 MB/s for the drive and 140MB/s for the array. Keep in mind this is an older Pentium D with the drives connected to an Supermicro LSI 1068 SAS controller.

My ESXi box has a RAID 10 of 4 x 500GB Western Digital RE3 drives on a PERC 6/i controller. The PERC is a Dell branded LSI controller. Inside the virtual machines I am getting 148MB/s. Unfortunately I can't test this at the ESXi level, but the MB/s will defiantly be higher as the virtual machine has another layer to go through.

Ryan

On Thu, Oct 29, 2009 at 3:25 PM, ML mailinglists@mailnewsrss.com wrote:

Ryan,

...

If you want performance stick with RAID 10. In general the more drives (spindles) the faster the array. The Western Digital RE3 500 GB drives are a good deal. You should be able to get 4 of those in the low $200s. In RAID 10 this would give you better performance than 2 x 1TB in RAID 1.

They are like $89.99 a  piece on NewEgg. I have a friend that has 1 x 1TB Seagate Raid level drives he will sell me for $100 each.

Is software RAID 10 decent performance?

-Jason

...

Ryan

On Thu, Oct 29, 2009 at 2:36 PM, ML mailinglists@mailnewsrss.com wrote:

...

On Oct 29, 2009, at 11:11 AM, Neil Aggarwal wrote:

...

RAID 10 is striping across mirrored drives.

So, if you have 4 x 1TB drives, think of it as two separate 1 TB volumes.  The system will write half your data to volume A and the other half to volume B.  The data in volume A and B do not overlap.

Now, each volume is composed of a mirrored set of drives. Anything written to volume A is actually stored on two drives. Anything written to volume B is actually stores on the other two drives.

Does this make sense? Let me know if you need any more explanation.

No it makes sense.

I am contemplating if I really need 4 x 1tb in this system. I mean how much space with some photo's, web pages and MySQL take up if there are 5,000 subscribers to start up?

Would 2 x 1TB enterprise drives be enough mirrored?

...

Also, when you move to a hosted solution, I would appreciate your considering my company for it.

Sure, I will be doing a lot of research on that for sure. _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos

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CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos

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CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos

Karan,

...

Also, when you move to a hosted solution, I would appreciate your considering my company for it.

I would highly recommend people consider companies that contribute and help with the project rather than those that dont.

Also, lets keep the soliciting for business off this list please.

Didn't you just contradict yourself?

How can we support companies that contribute and help the project if we don't know what each others companies do and specialize in?

-ML

On 10/29/2009 05:59 PM, Neil Aggarwal wrote:

If you want speed, use RAID 10.

Neil, you have been on the list long enough to know howto use it and work with the other people on the list, so keeping that in mind - dont top post.

most of the stuff coming from you just breaks the thread.

- KB

Curt Mills wrote:

On Thu, 29 Oct 2009, ML wrote:

...

My question is about initial setup. The 4 x 1TB drives. How to set this up for I have some protection?

RAID 0+1? (striped + mirrored) I would end up with 2TB useable space.

RAID 5? so what one is a hot spare? 3TB useable space?

What about striping the 4 1TB and mirroring that to a 4 x 1tb External drive enclosure?

Plan for drives going out but keeping the site operational. Also remember that RAID isn't a backup.

RAID 5 is enticing because you get more usable space out of your drives, but you have to be sure you'll only lose one drive at a time and can get a replacement drive in there and sync'ed up before you lose a 2nd one... If the drives were made by the same manufacturer and were bought at about the same time you might easily lose 2 or more, blowing up your array.

Right. The problem with 1TB drives (and really, any modern drive with decent capacity) is that you're vulnerable until that array finishes rebuilding-- a process that's taking longer and longer.

I'd go with the RAID10 solution that someone previously posited. By the time you outgrow that, you should really plan for a SAN/NAS solution anyway...

-- Corey / KB1JWQ