John J. Lee wrote:

On Thu, Apr 10, 2008 at 6:43 PM, Jerry Geis geisj@pagestation.com wrote:

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Hi all,

I was wonder what experiences there are out there with using RAID-X for performance increases. I do use RAID-1 (2 disks) but am interested in attemtps to gain higher R/W performance. Do the RAID-5's etc give noticeable performace increases?

A significant help for me was using ccache for compiling programs. That was a real performance increase.

Thanks for any suggestions/opinions.

jerry

If you want to higher R/W performance, you should go for raid0. raid0 fragments the data into the number of disks and distributes them. It gains a big performance. One drive fails, however, all data gone. raid5's benefit is not the speed but the effective space usage with the least data redundancy. Bitwise parity calculation consumes lots of processing power. So raid5 is the least choice in terms of performance.

-john

I had about the same interrogation a couple of months ago. I had to upgrade a mail server that was using a single IDE drive to store about 90 Gigs of mail, served by Communigate Pro on CentOS 4.6 (32 bits). The server was starting to crawl with high %iowait. The drive was simply a regular Western-Digital 7200 RPM 200 Gigs drives. Imagine the random access load, which is simply too much for a drive which is designed to handle single user load.

I finally set for 4 x Seagate SAS 73 Gigs 15000 RPM on RAID 10. The performance is very good. About 150-160 MiB/s througput R/W. We use an Adaptec 3405 (Unified SAS/SATA Crontroller, CentOS stock drivers) on a new Tyan Transport TA26 (B3992-E), 4 Gig RAM, Opteron 2214 & CentOS 5 x86_64.

I made tests with the same server in RAID 5. Read throughput was about the same but write was slightly lower (XOR Calculation) at about 135 MiB/s which is still real good. I chose RAID 10 because i had enough space with 146 Gigs RAID 10 and i wanted absolute throughput for our 50 e-mail users which use Outlook with Communigate MAPI Plugin. Sometimes they click on a big public sub-directory and sync between Outlook and the server takes place (local caching). The user are very satisfied and CentOS 5 is rock solid, providing a very good service since 2 months. The previous server run for about 3 years without any problem, providing excellent service even if it was running on modest hardware: Athlon XP 2500, Asus A7V600, 1 Gig RAM.

On another little project (friend's media file server), i assembled a cheap server with Asus M2N-e, Athlon Dual Core 4600+, 1 Gig DDR2 667 RAM , 40 Gigs IDE system drive and 4 x Western-Digital 500 Gigs RAID Editon (7200 RPM) data array. I used CentOS 5 x86_64 software RAID 5 (4 x 500 Gigs) and managed to get 35-40 MiB/s write throughput, which was much more than what he got using Intel ICH-8 RAID 5 on his Windoze PC (same drives). The Athlon DC 4600 handles the XOR very easily (low cpu usage) and the bottleneck seems to be on the bus (Regular PCI bus, 132 MiB/s max combined). He's absolutely satisfied with his new CentOS 5 Samba server. Combine that with WebMIN and a couple of scripts, he's stunned by how it's easy to use his server! I still wonder how people are paying for Winblows Home server...

Hope this helped a bit!

Guy Boisvert, ing. IngTegration inc.

I am currently running 7 raid10 data servers. I can say read speed increases but I doubt the write speed comparing to non raid setup. The main advantage of the raid is redundancy but not the performance. If you want to boost the disk performance, go for the faster drive with more than 10,000rpm spinning speed.

-john

On Thu, Apr 10, 2008 at 8:18 PM, Miguel Medalha miguelmedalha@sapo.pt wrote:

Have you tried RAID 10? It combines the security of RAID 1 with the speed of RAID 0. dmraid supports this RAID type.

...

I was wonder what experiences there are out there with using RAID-X for performance increases. I do use RAID-1 (2 disks) but am interested in attemtps to gain higher R/W performance. Do the RAID-5's etc give

noticeable performace increases?

...

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

Jason wrote:

John J. Lee wrote:

...

On Thu, Apr 10, 2008 at 8:18 PM, Miguel Medalha miguelmedalha@sapo.pt wrote:

...

...

I was wonder what experiences there are out there with using RAID-X for performance increases. I do use RAID-1 (2 disks) but am interested in attemtps to gain higher R/W performance. Do the RAID-5's etc give noticeable performace increases?

Have you tried RAID 10? It combines the security of RAID 1 with the speed of RAID 0. dmraid supports this RAID type.

I am currently running 7 raid10 data servers. I can say read speed increases but I doubt the write speed comparing to non raid setup. The main advantage of the raid is redundancy but not the performance. If you want to boost the disk performance, go for the faster drive with more than 10,000rpm spinning speed.

-john

while it takes a minimum of 6 disks, we've had great luck with RAID 50. Two separate RAID 5 arrays (fast read, moderate writes) that are then placed into a RAID 0 (fast read, fast write). you lose 2 drives worth of space, but lord it's fast and the data is mirrored. Not sure if you can do the whole thing in software. I use two 3Ware 9650SE cards to do the RAID 5 and I do RAID 0 in software.

The choice of a RAID setup really depends on the application it is used for and a RAID 50 or RAID 6 may be fast for a file server it will perform poorly for a database, mail or virtual machine server.

If your application is database, mail or virtualization guests then the way to go is RAID10.

The type of disk is important too. If you are doing file services on RAID5/50/6 then you may as well stick with SATA, but if you are doing database or mail then a SAS 10K drive may be in order depending on the amount of transactions or virtual machines, their type and applications they are running.

There is no one solution fits all unless you have the kind of money to buy SAS 10K RAID10s on hardware RAID with BBU write cache for everything.

Tell us what the application and hardware is, the number of clients, VMs or transactions/mails you plan on it handling and a best-cost solution can be provided.

BTW RAID50 can be done by adding 2 RAID5 PVs to a LVM VG and creating striped LVs across them. All by software.

-Ross

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