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Advice on allocating SSD
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  1. 24.11.2013 16:11:23
  2. # 1
Wesley Render Accepted Answer
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I just ordered an Intel SSD 910 PCIe 400GB card to increase the disk IO performance of our web hosting.  The server is a Xeon 5570 quad core, 8mb cache, with 48GB of memory, and 6 x 136GB SAS 15K Drives in a Raid 5 .  The server is running VMWare ESXi 5.1, and then we basically just have one virtual server with the following:

CloudLinux 6.4 x86_64
cPanel 11.40.x
All CPU Cores
48GB of Virtual Memory
375GB of disk space
10GB of MySQL Databases
90GB of web files

I am just wondering if anyone could advise on what would be the best approach to allocating the 400 of SSD space.  Would I simply install the card, have VMware pick up the space, add it as a new disk/partition to the cloudlinux virtual machine, and then move the MySQL Databases onto this partition?   Or would it be more effective to try and implement flashcache.  I'm just not sure if flashcache is a good solution when VMWare ESXi is in place.  The MySQL databases seem to be the only real bottleneck currently on the system.
  1. 24.11.2013 19:11:39
  2. # 2
Igor Seletskiy Accepted Answer
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As sad as it is - RAID5 is really bad thing for shared hosting. It will kill your performance, especially in relationship with MySQL & logs (RAID5 is terrible for lots of random writes)

You can try moving MySQL to a drive with SSD, but of course than you will not have RAID for MySQL.
Flashcache might be a better option - but the real thing (and probably the cause of MySQL being a bottle neck) is RAID5)
  1. 24.11.2013 19:11:24
  2. # 3
Wesley Render Accepted Answer
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Thanks Igor.  I did not realize RAID 5 was so bad for writes.  I think what I will do for now, is move MySQL onto a SSD partition.  You can do a mirror raid with the Intel 910 SSD Cards apparently, but I may not do that as we have a good backup systems in place, and the 910 SSD are supposed to be extremely reliable.  Eventually I guess I should be moving towards Raid 10, with all SSD drives?
  1. 25.11.2013 03:11:18
  2. # 4
Richard Hordern Accepted Answer
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Start with raid 1 with SSD drives and see if you need to move to raid 10 or not.

Also some ssd drives have a better integrated garbage collection if you don\'t format all the available space.
  1. 25.11.2013 13:11:55
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Gary Brooks Accepted Answer
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Seems to me that your going to loose more power from having a hypervisor in place for no good reason.  You should get rid of VMWare ESXi.   Go raw metal.
My advise is you Raid 10 the 6 drives, put mysql on raid 1 SSD (2 SSD's).   Also if you did not adjust your stripe size on your raid arrays, I would go for around 256k read blocks.   Make sure you enable read ahead on the adapter.

Also.. as far as loss data, you can easily backup mysql every 5 min with something like Idera backup software. The risk would be up to 5 min of loss data if your raid 1 failed on you.   
  1. 25.11.2013 13:11:24
  2. # 6
Richard Hordern Accepted Answer
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Sorry about the off subject but is idera more stable now ? My experience with it a bit over a year ago was bad (version 2 was OK but 3+ had alot of issues that encluded both agent and backup server crashing). I'm now worried about giving them another try…!
  1. 25.11.2013 13:11:30
  2. # 7
Gary Brooks Accepted Answer
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Richard,  

I have been through all the bumps with Idera and I have seen improvements in the product.   We have been a client for a little over 4 years.  We are happy with the way things have gone.  I think they had some hiccups while dealing with internal developer changes.   
  1. 25.11.2013 13:11:54
  2. # 8
Wesley Render Accepted Answer
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Hey thanks everyone.  Gary, I was running a bare metal OS before with CloudLinux, but there was a security bug in exim in cPanel that got compromised by spammers.   It was such a nightmare to get to the datacenter and get a new OS up and running, that I decided to implement VMWare ESXi with enough space that I could at anytime fire up a second virtual machine in case of emergency.  I did run some "hdparm" command tests before and after the virtualization and their was almost no performance loss in regards to disk io.   I think for now adding in the Intel 910 SSD, and then moving mysql onto that is the most feasible option.

I've been using Idera Server Backup Advanced now for a couple of years.  I have found it very reliable.  There were a couple of times when their software broke due to upgrades, but there support was helpful in getting things working.
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