Re: [CentOS] SSD drives for the OS - 1 or 2?

[Johnny Hughes]

On 01/04/2016 06:26 PM, Rob Kampen wrote:
> Preparing to build a small replacement server (initially built in 2005)
> and normally for the OS I would buy 2x500GB drives and deploy in a RAID
> 1 configuration.
> Now we have SSD drives available
> - does just a single SSD drive offer the same reliability or is there
> advantage in deploying two in a Raid 1 config?
> 
> Also, what form factor / interface is best for the SSD OS boot device on
> a server M/B? Anything I should be looking for?
> It seems most SSD are in laptop drive size, shape and interface - thus
> not a good fit into a server motherboard unless I'm missing something.
> - what devices are you using?
> 

A drive is a drive .. ssd's fail from time to time too.  While you may
not get the same rate of failure as with spinning disks, drives do fail
and the ability to shift seemlessly from one drive to another
automatically when using raid 1 far outweighs any disadvantages (which
is basically just double the cost for storage devices).

I would always use raid 1 on important devices.



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[CentOS] SSD drives for the OS - 1 or 2?

[Rob Kampen]

Preparing to build a small replacement server (initially built in 2005) 
and normally for the OS I would buy 2x500GB drives and deploy in a RAID 
1 configuration.

Now we have SSD drives available
- does just a single SSD drive offer the same reliability or is there 
advantage in deploying two in a Raid 1 config?


Also, what form factor / interface is best for the SSD OS boot device on 
a server M/B? Anything I should be looking for?
It seems most SSD are in laptop drive size, shape and interface - thus 
not a good fit into a server motherboard unless I'm missing something.

- what devices are you using?

Thanks in advance.
Rob
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Re: [CentOS] SSD drives for the OS - 1 or 2?

[Keith Keller]

On 2016-01-05, Rob Kampen  wrote:
> - does just a single SSD drive offer the same reliability or is there 
> advantage in deploying two in a Raid 1 config?

All else being equal, a RAID1 will be more reliable than a single drive,
whether it's magnetic or SSD.

> Also, what form factor / interface is best for the SSD OS boot device on 
> a server M/B? Anything I should be looking for?

If you're going for a RAID, you may as well also go for hot-swap drive
bays, so that you can change a failed drive without downing the system.
At that point you may as well ask your vendor what they suggest.  The
SSDs I have in a RAID1 configuration are 2.5" drives.

--keith

-- 
kkel...@wombat.san-francisco.ca.us


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Re: [CentOS] SSD drives for the OS - 1 or 2?

[Earl A Ramirez]

On 5 January 2016 at 09:26, Rob Kampen  wrote:

> Preparing to build a small replacement server (initially built in 2005)
> and normally for the OS I would buy 2x500GB drives and deploy in a RAID 1
> configuration.
> Now we have SSD drives available
> - does just a single SSD drive offer the same reliability or is there
> advantage in deploying two in a Raid 1 config?
>
> Also, what form factor / interface is best for the SSD OS boot device on a
> server M/B? Anything I should be looking for?
> It seems most SSD are in laptop drive size, shape and interface - thus not
> a good fit into a server motherboard unless I'm missing something.
> - what devices are you using?
>
> Thanks in advance.
> Rob
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There will always be advantages in using Raid 1 for OS, but to be able to
give you a better response, we will need a little more information.

We currently use SSDs on our blade servers, which uses hardware raid 1 for
the OS only and most data and other applications are configured on
different drives/clusters.

-- 
Kind Regards
Earl Ramirez
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Re: [CentOS] SSD drives for the OS - 1 or 2?

[John R Pierce]

On 1/4/2016 4:26 PM, Rob Kampen wrote:
It seems most SSD are in laptop drive size, shape and interface - thus 
not a good fit into a server motherboard unless I'm missing something.
- what devices are you using? 



server motherboards don't care what size the drives are, that's a 
function of your server *chassis*.You can always put a 2.5" drive in 
a 3.5" adapter, but many modern servers are designed specifically for 
2.5" drives, especially servers using SAS.


example, note the two servers on the top of the closer rack.
https://pierce.smugmug.com/By-Date/2012/2012-02-09/i-8WfCvLJ/0/X3/IMG_0318-X3.jpg

those are HP DL180g6, each holds 25 2.5" SAS hotswap drives in a 2U form 
factor.


I *do* recommend getting 'enterprise' grade SSDs that have 'supercaps' 
to ensure they can flush their write buffers on a power failure.




--
john r pierce, recycling bits in santa cruz

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Re: [CentOS] SSD Drives

[Michael Simpson]

On 2 February 2012 18:19, Matt matt.mailingli...@gmail.com wrote:
 Has anyone installed a high I/O application such as an email server on
 SSD drives?  Was thinking about doing two SSD's in RAID1.  It would
 solve my I/O latency issues but I have heard that SSD's wear out
 quickly in high I/O situations?  Something like each memory location
 only has X many writes before its done.  Just wandering if anyone has
 tested it and if newer SSD's are better about this?

Sun were recommending using SSDs for the ZIL in really big ZFS install
*years ago* so go for it.

As long as you are using TRIM then you avoid the slowdown that happens
once the ssd is full

http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/newmds-ssdtuning.html

mike
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Re: [CentOS] SSD Drives

[Nataraj]

On 02/02/2012 10:19 AM, Matt wrote:
 Has anyone installed a high I/O application such as an email server on
 SSD drives?  Was thinking about doing two SSD's in RAID1.  It would
 solve my I/O latency issues but I have heard that SSD's wear out
 quickly in high I/O situations?  Something like each memory location
 only has X many writes before its done.  Just wandering if anyone has
 tested it and if newer SSD's are better about this?
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Is this the best way to go?  Much of the recent mail software, postfix,
dovecot etc has features which make it easier to set up redundant
mailservers and distribute the load across them.  This will scale better
if your needs grow down the road.  SSD's tend to be rather costly,
especially if your storage needs are high.   I guess the main advantage
to a single server with SSD is lower power consumption.

What about RAID10?

Nataraj

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Re: [CentOS] SSD Drives

[William Warren]

On 2/2/2012 5:19 PM, Peter A wrote:
 On 02/02/12 17:01, William Warren wrote:
 On 2/2/2012 2:15 PM, Peter A wrote:
 If you're worried about io reliability, then buy a (way more expensive)
 SLC drive, rather than the consumer level MLC... We have some SLC drives
 here that from their manufacturer have been rated at 3 or more years of
 100% write 24x7...

 Peter.

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 exactly hence why i said stay with OCZ or Intel..MLC drives are the
 best.  But also the smaller the process node the shorter the lifespan of
 the flash.  MLC drives will also over provision more spare flash area
 most times.
 Aeh... that's exactly the opposite of what I said. MLC (multi level
 cell) SSDs store more than one bit per cell. In current devices that's
 mostly 2 bits per cell, but more is around the corner. On an SLC (single
 level cell) there is only one bit per cell - true binary just like what
 we have in RAM and others. SLC devices are superior in reliability
 because it simply takes a lot more disturbing of a cell to make it lose
 enough charge that a 1 gets interpreted as a 0. The devices are also
 usually faster, especially on a re-write basis.
 A Oracle 96GB flash card (SLC) physically has 128GB. Most consumer MLC
 devices with 128GB are sold as 120GB visible... Again in favor of the
 SLC. Only problem is that you pay for what you get. SLC devices are
 significantly more expensive. Fusion I/O and all the other server ssd
 vendors do the same - they give you a cheap MLC device with limited
 performance and reliability and a high end, much more pricey SLC unit.

 Peter.
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i mistyped meant to type slc...:)
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[CentOS] SSD Drives

[Matt]

Has anyone installed a high I/O application such as an email server on
SSD drives?  Was thinking about doing two SSD's in RAID1.  It would
solve my I/O latency issues but I have heard that SSD's wear out
quickly in high I/O situations?  Something like each memory location
only has X many writes before its done.  Just wandering if anyone has
tested it and if newer SSD's are better about this?
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Re: [CentOS] SSD Drives

[William Warren]

On 2/2/2012 1:19 PM, Matt wrote:
 Has anyone installed a high I/O application such as an email server on
 SSD drives?  Was thinking about doing two SSD's in RAID1.  It would
 solve my I/O latency issues but I have heard that SSD's wear out
 quickly in high I/O situations?  Something like each memory location
 only has X many writes before its done.  Just wandering if anyone has
 tested it and if newer SSD's are better about this?
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it all depends on how much writing you do AND how much spare space the 
drives have.  The more spare flash the drives have the longer they'll 
live due to being able to spread the writing wear over a larger area.
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Re: [CentOS] SSD Drives

[Mike]

On Thu, 2 Feb 2012, William Warren wrote:

 On 2/2/2012 1:19 PM, Matt wrote:
 Has anyone installed a high I/O application such as an email server on
 SSD drives?  Was thinking about doing two SSD's in RAID1.  It would
 solve my I/O latency issues but I have heard that SSD's wear out
 quickly in high I/O situations?  Something like each memory location
 only has X many writes before its done.  Just wandering if anyone has
 tested it and if newer SSD's are better about this?

 it all depends on how much writing you do AND how much spare space the
 drives have.  The more spare flash the drives have the longer they'll
 live due to being able to spread the writing wear over a larger area.

How very timely, I'm just starting to investigate something similar 
myself.  I don't have much to contribute however this forum post:
http://www.xtremesystems.org/forums/showthread.php?271063-SSD-Write-Endurance-25nm-Vs-34nm
seems as though it'll be interesting, if I can ever make it through 3500+ 
pages to get to the conclusion.

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Re: [CentOS] SSD Drives

[Peter A]

On 02/02/12 14:05, Mike wrote:
 On Thu, 2 Feb 2012, William Warren wrote:

 On 2/2/2012 1:19 PM, Matt wrote:
 Has anyone installed a high I/O application such as an email server on
 SSD drives?  Was thinking about doing two SSD's in RAID1.  It would
 solve my I/O latency issues but I have heard that SSD's wear out
 quickly in high I/O situations?  Something like each memory location
 only has X many writes before its done.  Just wandering if anyone has
 tested it and if newer SSD's are better about this?

 it all depends on how much writing you do AND how much spare space the
 drives have.  The more spare flash the drives have the longer they'll
 live due to being able to spread the writing wear over a larger area.

 How very timely, I'm just starting to investigate something similar
 myself.  I don't have much to contribute however this forum post:
 http://www.xtremesystems.org/forums/showthread.php?271063-SSD-Write-Endurance-25nm-Vs-34nm
 seems as though it'll be interesting, if I can ever make it through 3500+
 pages to get to the conclusion.

If you're worried about io reliability, then buy a (way more expensive) 
SLC drive, rather than the consumer level MLC... We have some SLC drives 
here that from their manufacturer have been rated at 3 or more years of 
100% write 24x7...

Peter.

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Re: [CentOS] SSD Drives

[William Warren]

On 2/2/2012 2:15 PM, Peter A wrote:
 On 02/02/12 14:05, Mike wrote:
 On Thu, 2 Feb 2012, William Warren wrote:

 On 2/2/2012 1:19 PM, Matt wrote:
 Has anyone installed a high I/O application such as an email server on
 SSD drives?  Was thinking about doing two SSD's in RAID1.  It would
 solve my I/O latency issues but I have heard that SSD's wear out
 quickly in high I/O situations?  Something like each memory location
 only has X many writes before its done.  Just wandering if anyone has
 tested it and if newer SSD's are better about this?

 it all depends on how much writing you do AND how much spare space the
 drives have.  The more spare flash the drives have the longer they'll
 live due to being able to spread the writing wear over a larger area.

 How very timely, I'm just starting to investigate something similar
 myself.  I don't have much to contribute however this forum post:
 http://www.xtremesystems.org/forums/showthread.php?271063-SSD-Write-Endurance-25nm-Vs-34nm
 seems as though it'll be interesting, if I can ever make it through 3500+
 pages to get to the conclusion.

 If you're worried about io reliability, then buy a (way more expensive)
 SLC drive, rather than the consumer level MLC... We have some SLC drives
 here that from their manufacturer have been rated at 3 or more years of
 100% write 24x7...

 Peter.

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exactly hence why i said stay with OCZ or Intel..MLC drives are the 
best.  But also the smaller the process node the shorter the lifespan of 
the flash.  MLC drives will also over provision more spare flash area 
most times.
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Re: [CentOS] SSD Drives

[Peter A]

On 02/02/12 17:01, William Warren wrote:
 On 2/2/2012 2:15 PM, Peter A wrote:
 If you're worried about io reliability, then buy a (way more expensive)
 SLC drive, rather than the consumer level MLC... We have some SLC drives
 here that from their manufacturer have been rated at 3 or more years of
 100% write 24x7...

 Peter.

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 exactly hence why i said stay with OCZ or Intel..MLC drives are the
 best.  But also the smaller the process node the shorter the lifespan of
 the flash.  MLC drives will also over provision more spare flash area
 most times.
Aeh... that's exactly the opposite of what I said. MLC (multi level 
cell) SSDs store more than one bit per cell. In current devices that's 
mostly 2 bits per cell, but more is around the corner. On an SLC (single 
level cell) there is only one bit per cell - true binary just like what 
we have in RAM and others. SLC devices are superior in reliability 
because it simply takes a lot more disturbing of a cell to make it lose 
enough charge that a 1 gets interpreted as a 0. The devices are also 
usually faster, especially on a re-write basis.
A Oracle 96GB flash card (SLC) physically has 128GB. Most consumer MLC 
devices with 128GB are sold as 120GB visible... Again in favor of the 
SLC. Only problem is that you pay for what you get. SLC devices are 
significantly more expensive. Fusion I/O and all the other server ssd 
vendors do the same - they give you a cheap MLC device with limited 
performance and reliability and a high end, much more pricey SLC unit.

Peter.
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