Message: 67 Date: Fri, 11 May 2007 11:40:25 +0800 From: Feizhou feizhou@graffiti.net Subject: Re: [CentOS] Re: Anaconda doesn't support raid10 To: CentOS mailing list centos@centos.org Message-ID: 4643E5A9.3030302@graffiti.net
Feizhou wrote: <snip>
The SCSI drive: Spindle Speed 15000 rpm Average latency 2.0 msec Random read seek time 3.50 msec Random write seek time 4.0 msec
The SATA drive: Spindle Speed 7200 rpm Native Command Queuing Y Average latency 4.16 msec Random read seek time <8.5 msec Random write seek time <10.0 msec Maximum interface transfer rate 300 Mbytes/sec
Compare to a 10K scsi drive: Spindle Speed 10,000 rpm Sustained data transfer rate 80 Mbytes/sec. Average latency 3.0 msec Random read seek time 4.9 msec Random write seek time 5.4 msec Maximum interface transfer rate 320 Mbytes/sec
The above specifications are about Performance. If maximum Reliability is the goal, look at the MTBF in the specifications. If the Design Engineers have done their job, and the Manufacturing Engineers maintain high Quality Control, the result should be a quality component.
As has been pointed out in this thread, RAID is *not* a substitute for backups. RAID is intended to keep the box up and running. Valuable data should always be stored off site, in removable drives, or via the WAN. Lanny
The above specifications are about Performance. If maximum Reliability is the goal, look at the MTBF in the specifications. If the Design Engineers have done their job, and the Manufacturing Engineers maintain high Quality Control, the result should be a quality component.
I am sorry but for quite a while already, both PATA/SATA/SCSI drives have been sharing the same manufacturing technology. So while the specifications of the different disks are different, the reliability factor has been proven to be the same across the board. You must have missed the thread on the Google report on various drives that they use which is also what I see in my previous job at an ISP that has over 40 million mailboxes. SCSI is only needed when disk i/o is really critical and that is assuming you cannot use large battery backed up RAM drives/write caches to mitigate the slower disk performance.
No matter what kind of drive you have, if you get constant changes in temperature, that disk is going to die much sooner than its supposed lifetime.
As has been pointed out in this thread, RAID is *not* a substitute for backups. RAID is intended to keep the box up and running. Valuable data should always be stored off site, in removable drives, or via the WAN.
Who says? You? I like to have an online offsite RAID backup server. Is there an ONE TRUE WAY OF BACKUP?
Feizhou wrote:
As has been pointed out in this thread, RAID is *not* a substitute for backups. RAID is intended to keep the box up and running. Valuable data should always be stored off site, in removable drives, or via the WAN.
Who says? You? I like to have an online offsite RAID backup server. Is there an ONE TRUE WAY OF BACKUP?
No, but if there is one way it can fail, you can bet it will - and at the worst possible time.
Am Dienstag, 15. Mai 2007 schrieb Feizhou:
As has been pointed out in this thread, RAID is *not* a substitute for backups. RAID is intended to keep the box up and running. Valuable data should always be stored off site, in removable drives, or via the WAN.
Who says? You? I like to have an online offsite RAID backup server. Is there an ONE TRUE WAY OF BACKUP?
I think the point is that RAID is not a substitute for backups. That does not imply what backup technique to use. Making Backups to another server that also uses RAID is absolutely reasonable IMHO. We do just that around here.
However it can not be stressed enough that just putting RAID-1 or RAID-5 into a server is not a substitute for backups.
Am Dienstag, 15. Mai 2007 schrieb Feizhou:
However it can not be stressed enough that just putting RAID-1 or RAID-5 into a server is not a substitute for backups.
Hear hear
What exactly is your problem?
From the Software RAID HOWTO: --------------------------------------------------------------------------- 2. Why RAID?
There can be many good reasons for using RAID. A few are; the ability to combine several physical disks into one larger "virtual" device, performance improvements, and redundancy.
It is, however, very important to understand that RAID is not a substitute for good backups. Some RAID levels will make your systems immune to data loss from single-disk failures, but RAID will not allow you to recover from an accidental "rm -rf /". RAID will also not help you preserve your data if the server holding the RAID itself is lost in one way or the other (theft, flooding, earthquake, Martian invasion etc.)
RAID will generally allow you to keep systems up and running, in case of common hardware problems (single disk failure). It is not in itself a complete data safety solution. This is very important to realize. ---------------------------------------------------------------------------
Source: http://tldp.org/HOWTO/Software-RAID-HOWTO-2.html
On Tue, May 15, 2007 at 12:13:48PM +0200, Andreas Micklei enlightened us:
Am Dienstag, 15. Mai 2007 schrieb Feizhou:
However it can not be stressed enough that just putting RAID-1 or RAID-5 into a server is not a substitute for backups.
Hear hear
What exactly is your problem?
Likely only expecting everyone is a native English speaker. "Hear hear" is sorta like a +1 to what you said.
Matt
Am Dienstag, 15. Mai 2007 schrieb Matt Hyclak:
On Tue, May 15, 2007 at 12:13:48PM +0200, Andreas Micklei enlightened us:
Hear hear
What exactly is your problem?
Likely only expecting everyone is a native English speaker. "Hear hear" is sorta like a +1 to what you said.
Ah, ok. :-D Thanks for pointing out.
Andreas Micklei wrote:
Am Dienstag, 15. Mai 2007 schrieb Matt Hyclak:
On Tue, May 15, 2007 at 12:13:48PM +0200, Andreas Micklei enlightened us:
Hear hear
What exactly is your problem?
Likely only expecting everyone is a native English speaker. "Hear hear" is sorta like a +1 to what you said.
Ah, ok. :-D Thanks for pointing out.
;) Sorry :P
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