RX1330M1

PRIMERGY, SPARC Enterprise Server, PRIMEFLEX, PRIMEPower, BS2000

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spzsoft
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Joined: Sun May 08, 2016 15:43
Product(s): Primergy Servers

RX1330M1

Postby spzsoft » Mon May 09, 2016 9:59

I have a RX1330M1/LFF/HOT with 2 WD 1TB B.C. yellow sata hd in raid 1 configuration on LSI embedded MegaRAID controller. The write performance of the volume are very poor the writing tail is often full.
Sorry I have some questions:
If I active the "disk cache mode" I have an improvement of the performance ?
Can I do this (on/off the cache mode) in production environment without any problem ?
Have the embedded megaraid a backup battery in caso of power failure ?
If No the power failure with cache mode active what does ?
Beast Regard
Basilio

Davie
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Re: RX1330M1

Postby Davie » Mon May 09, 2016 13:43

The embedded MegaRAID has no cache on the motherboard, so no controller caching is possible.

The disks themselves have cache within the disk (maybe 64Mb who knows...) but there is nothing, batteries or anything else that protects that cache in event of a power failure - so if you have power fail then you risk losing all that data in the disk cache that may not have been written to the magnetic media yet.

Not really advisable if you care about your data. If you are using it as a scratch volume then ok...

me@work
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Joined: Thu Jun 22, 2006 15:32
Product(s): Scaleo Pi2662, Primergy

Re: RX1330M1

Postby me@work » Mon May 09, 2016 13:47

- Embedded MegaRAID does not "need" a BBU, because it does not feature any cache that would need to be protected against power failure.
- Disk cache (Read it thoroughly! It's DISK, not controller!:-)) mode can be changed during normal operation without harming any data transfers.
- With those 7200rpm SATA drives, you will most definitely see an improvement in performance. Whether it suffices your requirements, is to be tested & verified.
- Of course, in case of a power failure, all data sitting in the disks' cache and not having been written to the disks' media will be lost. Even with a SAS RAID contraller WITH cache AND BBU, only the controller's caches will be protected. The disks' caches can only be protected by eliminating the risk of a power problem, e.g. with a UPS, and by keeping all fingers crossed that no controller problems will ever happen.

PS:
Sorry for mostly repeating Davie's comment, I was too slow.

Davie
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Location: UK

Re: RX1330M1

Postby Davie » Mon May 09, 2016 14:44

Even a UPS isn't guaranteed to help. You may protect again power fail but what if PSU fails? Or with redundant PSUs, a fault on power backplane?

spzsoft
Posts: 2
Joined: Sun May 08, 2016 15:43
Product(s): Primergy Servers

Re: RX1330M1

Postby spzsoft » Mon May 09, 2016 18:39

If I understand, to reduce the risk at least one of the power supply should be connected to an UPS able to send at the server the message "battery low" and then the server make a regular shutdown otherwise ...."keeping all fingers crossed"
I understand I can still change, for testing, the Disk Cache parameter without any data loos or other problem.

revolgk
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Joined: Mon May 09, 2016 10:04
Product(s): Primergy Servers

Re: RX1330M1

Postby revolgk » Tue May 10, 2016 11:22

in my experience SATA disks and disk cache enabled gave an impressive performance improvement
BUT you have NO data security
a cheeper option to an external UPS for your system is the FJBU Fujitsu battery unit
this goes in instead of the 2nd PSU and is charged when the system is running
if the 1st psu fails then the FJBU will keep the system up so a shutdown can happen,the associated software will cause the system shutdown
and the system cannot restart until the first PSU is working again
I have tested this on my system IF you want to go this way and have problems let me know I have a document on how to get it working screen shots etc
regards
Kenneth

me@work
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Joined: Thu Jun 22, 2006 15:32
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Re: RX1330M1

Postby me@work » Tue May 10, 2016 16:59

Plus, you must not use one single UPS device to connect both PSU in the server, as in that case, the UPS would be a Single Point of Failure...

So the reading should be "exactly" instead of "at least", if you don't use TWO UPS device, or if they're not connected to two different power circuits (or plants...)


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