Hi,
As always it depends on what kinds of workload these machines do.
Webserving alone is usually not a very (disk) IO intensive task as the
most commonly hit files are kept in memory.
Databases are a different story however as are fileservers (naturally)
It might make sense to separate the databases onto a separate array or
run those on local disks.
What I'm doing is have all webservers on DomU's off an iSCSI array and
have the databases in separate DomU's running off the servers' local
disks.
This keeps the performance of the databases predictable, latency low
and takes a big chunk of IO out of the iSCSI.
Regards,
Barry
>
> we have 7 Servers with about 30 VM spread accross these servers.
> Would a iSCSI device with 1Gb/1GB Interface enaough to hold up to 100VM?
> Or will the IO be not enough? Most VM do serve websites, but some have
> heavy mysql usage.
>
> thx
>
>>
>> Also, I cannot stress enough the importance of a decent raid card,
>> spread the VMs across multiple raid 1 arrays and a decent SAS card
>> should let you mix and match SAS and SATA drive arrays which is often
>> convenient.
>>
>> -----Original Message-----
>> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
>> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Rudi Ahlers
>> Sent: 23 January 2009 12:53
>> To: Craig Herring
>> Cc: xen-users
>> Subject: Re: [Xen-users] Optimizing I/O
>>
>> If possible, add as many disks to the machine as it can take, and
>> spread the VM's out across the disks / partitions.
>>
>> Or, if you can, setup RAID 10 to help load the IO of different data
>> onto different disks / controllers. Don't use IDE, and try and get the
>> fastest disks for your budget. SATA II isn't that much more expensive
>> than IDE. Or if you can afford it, and the mobo can handle it, get
>> SCSI or SAS drives.
>>
>> On Fri, Jan 23, 2009 at 7:03 AM, Craig Herring <craigeherring@xxxxxxxxx>
>> wrote:
>>> I've found the biggest issue with virtualization is disk I/O. NIC I/O
>> I have
>>> not seen much of an issue especially if you are using a GB nic. If you
>> are
>>> having issues with NIC IO this would indicate you are possibly
>> approaching
>>> 120MB/sec. Although use separate NICs for your different networks or
>> bond
>>> them with ALB can help. If you are using NFS or iSCSI storage use
>> different
>>> NICs than your guest networks. Also a good quality switch can assist
>> as
>>> well, even sometimes overlooked. A good quality HP 1800 series switch
>> isn't
>>> expensive at all. I've seen some tests that suggest Intel NICs have
>> less
>>> latency, almost half, than most others.
>>>
>>> In most situations I find running a RAID 1 / RAID 10 and using less
>> than 5
>>> VMs per partition is a good rule of thumb to stay away from disk
>> contention
>>> issues. Also using iSCSI and DRBD can assist in speed as this would
>> dedicate
>>> a server to handling disk IO. These services can also use much of the
>> ram as
>>> cache. Stay away from the *fake* RAID stuff or even the cheap RAID
>>> controllers. Buy the better later gen 3WARE, LSI, Areca controllers or
>> just
>>> use software RAID. Also format the partition XFS and set the noatime
>> flag.
>>> The WD RE3/2/Raptor drives are incredibly fast especially in a RAID 1.
>>>
>>> -Craig
>>>
>>> lists@xxxxxxxxxxxx wrote:
>>>>
>>>> My question was really meant to ask about I/O, in as far as file
>>>> transferring between main host and network for host and guests but
>> anything
>>>> is good.
>>>> Just trying to pull all my questions and notes together so that I can
>> get
>>>> on this in a week or two and it's good to see folks sharing their
>> ideas,
>>>> methods etc.
>>>>
>>>> So for example, on a system that's pretty much RPM based, what tweaks
>> can
>>>> someone make to the various configurations files which would greatly
>> help
>>>> overall network I/O.
>>>>
>>>> Mike
>>>>
>>>>
>>>> _______________________________________________
>>>> Xen-users mailing list
>>>> Xen-users@xxxxxxxxxxxxxxxxxxx
>>>> http://lists.xensource.com/xen-users
>>>>
>>>
>>>
>>> _______________________________________________
>>> Xen-users mailing list
>>> Xen-users@xxxxxxxxxxxxxxxxxxx
>>> http://lists.xensource.com/xen-users
>>>
>>
>>
>>
>> --
>>
>> Kind Regards
>> Rudi Ahlers
>>
>> _______________________________________________
>> Xen-users mailing list
>> Xen-users@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-users
>>
>> The SAQ Group
>>
>> Registered Office: 18 Chapel Street, Petersfield, Hampshire GU32 3DZ
>> SAQ is the trading name of SEMTEC Limited. Registered in England & Wales
>> Company Number: 06481952
>>
>> http://www.saqnet.co.uk AS29219
>>
>> SAQ Group Delivers high quality, honestly priced communication and I.T.
>> services to UK Business.
>>
>> Broadband : Domains : Email : Hosting : CoLo : Servers : Racks : Transit :
>> Backups : Managed Networks : Remote Support.
>>
>> ISPA Member
>>
>> Find us in http://www.thebestof.co.uk/petersfield
>>
>>
>> _______________________________________________
>> Xen-users mailing list
>> Xen-users@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-users
>>
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-users
>
--
Barry van Someren
---------------------------------------
Email: barry@xxxxxxxxxxxxxxx
Email: goltharnl@xxxxxxxxx
_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users
|
Home