2 VMs: 2x RAID 1 or 1x RAID 10

[Pete248]

I'm in the step of combining 2 older servers into a newly setup ESXi 4 Server.

Hosted VMs will be:

1 Linux System (Debian) for Webserver, Mailserver, MySQL, Bind.

1 Windows XP or 7 solely for a proprietary database system.

At first I thought about combining 4x 10000 rpm SATA drives into a RAID 10 and run ESXi + VMs from that RAID.

But probably using a dedicated RAID 1 for each VM might give a more reliable performance for each VM. The speed advantage of the RAID 10, mainly high sustained data transfer speed, might not bring much advantage, as the type of services I'll run on either VM IMHO benefit more from fast access times for reading/writing small files, than from high sustained data transfer speed for reading/writing big files.

What is your opinion?

Furthermore where would you install the ESXi hypervisor? Options would be the RAID 10, one of the two RAID 1 or onto a DOM/USB stick. Performance-wise it seems to make no difference, as the Hypervisor, once booted, seems to run in RAM without generating much disk access, right? So it is probably more a question of freedom in flexibility to change the RAID configurations.

Thanks for any comments.

Pete

[AntonVZhbankov]

RAID 10 will give you more peak performance, and you can limit IOPS on VM-level to prevent one VM from stealing all the performance if needed.

Install ESXi on USB flash.

---

MCITP: SA, MCTS Hyper-V, VCP 3/4, VMware vExpert

http://blog.vadmin.ru

[Nikhil_Patwa]

Hi,

Creating 2 RAIDs will create 2 datastores within your ESXi, you can install your ESXi in any of your RAIDS/Datastore.

Since you have 4 hard drives why don't you create RAID5 and put all your VMs in the same datastore.

Personally I would prefer to create a single RAID (of your choice) and copy/create all your VMs.

Creating 2 X RAID 1 will use 2 of your hard drives for RAID configuration and allow you only 2 drives and that also not combined but separate therefore you datastore size will also be the size of your hard drive.

Hope this information is useful to you

Nikhil

[golddiggie]

I second Anton's suggestion of RAID 10 and using an USB flash drive (2-8GB in size) for ESXi 4.x...

4 drives on RAID 10 will outperform the same 4 drives under RAID 5...

VMware VCP4

Consider awarding points for "helpful" and/or "correct" answers.

[Pete248]

RAID 10 will give you more peak performance, and you can limit IOPS on VM-level to prevent one VM from stealing all the performance if needed.

Thanks. I wasn't aware of the IOPS limiting option in ESXi. Have to check on this.

Question is: If I give each VM 50% IOPS of a unified RAID 10, wouldn't that be the same max. IOPS as giving each VM it's dedicated RAID 1?

Install ESXi on USB flash.

Yes, that's what I planned to do. Only issue might be, the server would fail to restart in case the USB flash gets corrupted. I've never heard of USB sticks with internal RAID 1.

Would it work to install 2 sticks with mirrored content and set them as the first two boot devices in BIOS? So if the first fails, the machine could boot from the second one.

Pete

[Pete248]

Since you have 4 hard drives why don't you create RAID5 and put all your VMs in the same datastore.

I'm aware of the benefit of RAID 5 in wasting less drives for redundancy and the easy expandability of the array. But from all what I read, RAID 5 is not recommended for database- or mailservers, or in general for writing many small files to the array. Thus I've picked RAID 10 (vs. RAID 1) in this thread.

The ideal usage of a RAID 5 shall be for streaming media files or as a backup server, neither I plan to do with this server.

Pete

[Pete248]

I second Anton's suggestion of RAID 10 and using an USB flash drive (2-8GB in size) for ESXi 4.x...

Thanks, I appreciate your post, although you recommend the same as Anton, as it gives me an impression, what the common recommendation is.

Concerning USB flash drive (2-8GB). I've read 1 GB would be enough. So I'd rather go for a faster 2 GB than for a 8 GB. Any benefits to use one > 2GB?

4 drives on RAID 10 will outperform the same 4 drives under RAID 5...

That's what I expected anyways. The question was, whether a dedicated RAID 1 for each VM would outperform a unified RAID 10 containing both VMs.

Pete

PS: As I plan to use a perc 5/i in the server, I've stepped over this benchmark (see diagrams in the middle of the page):

http://www.overclock.net/raid-controllers-software/359025-perc-5-i-raid-card-tips-432.html

Seems like RAID 5 gives much better performance than RAID 10 for writing large files and only slightly less performance for writing small files. Strange!

[golddiggie]

I've never trusted the 'would be enough' parameters when it comes to important things such as where to install ESX/ESXi... While you might be able to get away with a 1GB flash drive, I know that ESXi 4 installs, and runs, very well on a 2GB flash drive. I've also installed ESXi 4.1 onto a 4GB flash drive and had zero issues during the install as well as running from it. I used SanDisk Cruzer model flash drives (different generations between the two ESXi installs)... I used one of the newer models (plastic housing) for ESXi 4.1, the older was one of the original titanium models. I would use SandDisk flash drives before any other manufacturer for this (it's one of the few brands I have actually)... You can get the 4GB model for such cheap money these days (about $11 on newegg.com), it's not even funny (especially compared with what I got mine for)... If you need it immediately, then go to Staples and get it for about $20 (best buy has it for $30)... Amazon has it for a little more than newegg... Model is SDCZ36-004G-A11...

I've never had a SanDisk Cruzer flash drive go bad on me. If you're concerned, then install ESXi 4.x onto a second one during your install process (or use a second host server to do it while installing onto the other) and keep it in reserve. Hell, you could get a handful of them and have them in the wings in case something does go bad on you...

Personally, I would use external USB ports if at all possible for the flash drive. That way you don't have to worry (at all) about temperatures getting too high for the device.

I use the ESXi flash drives more for testing than anything else right now... I might use that option for my next ESXi host, but then again I might just get a small SSD drive and install onto that. You can get a 30GB SSD for cheap money these days...

VMware VCP4

Consider awarding points for "helpful" and/or "correct" answers.

[Pete248]

Thanks for all comments.

I'll go with 4GB flash memory for the ESXi install and RAID10 for the VM storage.

Pete

[ITatRTM]

Keep in mind that sometimes you will just need to test, blow away your config, reload, and test again. Then compare the results.

Considering that installing ESXi is a very quick process, we tested all RAID configs available on our new HP DL380 for R/W performance before rolling out the server for production. We used the same Server 2003 VM, and just kept reloading it from backup after each RAID config change.

[wm408]

ITatTRM,

     What did you find with your testing with the different raid configs??

     When everyone in this thread discusses "VM" space, are we also including storage for those VMs as well?

     I have an HP DL360 G5.  It has 6 drive bays on a Smart Array P400i.  I was thinking about ESXi embedded on an external flash.  How do you guys

     recommend I use the 6 bays?  The spec says: RAID 0/1/1+0/5/6 for the smart array P400i.

     I want the server to host an accounting solution (MAS200, and its data), a terminal server to support about 15-20 users, and possibly a win2k DC with        light to moderate active directory requests. 

     Thanks

[Josh26]

The performance modifier on a P400i controller is the size of the battery of flash backed write cache purchased with it, far more than the RAID level.

By the way, bumping old threads on this forum is not generally as useful as starting a new one.

[wm408]

Josh,

     Thanks for your reply.  Sorry about the bump, I just try to work with what is available first before opening new topics on similar topics.

     About the write back cache, there is an optional 512 BBWC.  I am not sure on what mine is just yet, looking into that.  Is this decent?

     Do you have thoughts on what RAID config I should use?  And is it ok to have the VMs on the same logical drive as data for the VMs?

Thanks

[Josh26]

The 512MB BBWC would be the minimum current requirement.

For new, current gen servers I would recommend a 1GB cache.

There is no problem operating VM OS and VM data on the same LUN LUN. By all means, create separate vdisks to break up space appropriately.

[wm408]

Great, thanks for the advice.  You still haven't recommended a RAID configuration .  Would 1+0 be ok?  I have 6 slots. 

[Josh26]

Hi,

RAID1+0 would be fine, as would RAID5 if you would like more capacity.

[J1mbo]

Just be sure the controller can provide LUNs under the 2TB limit (only an issue with 700GB+ disks, with six drives).

Some controller won't break RAID-x0 volumes, which forces the use RAID-6 instead.

[wm408]

I'm thinking a RAID 1+0 with 5 drives now.  The 5th drive as a Hot Spare.  Each drive is HP 300GB 3G SAS 10K SFF DP ENT HDD.  So I would have 600GB total, I stay just under your 700+GB mark, and 5 drives instead of 6.  Not to avoid this thought, but just because I don't need 6 now.  

Thanks for the thoughts.