Re: [Bacula-users] Bacula spool on SSD -- solid state drive?performance testing?

[<ran...@bi...>]

Let me give you guys the skinny on what an engineer told me who deals a lot with SSDs.  They do have limited read write cycles.  Under "normal" usage, they last about five years.  So I would have to agree with Kevin on this one.  

On our backup system, the spool drives are used heavily and I would not consider it "normal" usage.  Basically, your expensive ssd drives are not going to last very long in this kind of setup.  SSD's make good system drives and good laptop drives where the read and write cycle is more "normal".  Of course, do not get me wrong, the performance gains of SSDs is very appealing and I have caught myself considering their application a time or two.

Of course, the price of SSD's may drop as economy of scales becomes more apparent and SSD's move further along in the product lifecycle curve.  If I had to make a choice right now, I would go with 15K RPM drives and a good RAID controller.  Now five years from now, I would probably recommend something else, but that is why we all love technology, right?

Randall Svancara
Systems Administrator/DBA/Developer
Main Bioinformatics Laboratory



----- Original Message -----
From: "Kevin Keane" <sub...@kk...>
Cc: "Bacula-Users" <bac...@li...>
Sent: Friday, July 24, 2009 3:19:22 PM GMT -08:00 US/Canada Pacific
Subject: Re: [Bacula-users] Bacula spool on SSD -- solid state drive?performance testing?

John Lockard wrote:
> For spool, I would worry about the limited write (erase) cycles of 
> SSD. Sure, the speed of read/write is enormously appealing, but with 
> how much my spool gets hit I'd hate to have to set a really early 
> replacement schedule because my media can't handle many writes.  
> Rather than SSD for spool, RAM-Disk looks like a better way to go.
I'm wondering about that. I haven't actually done any research into it, 
but I would have assumed that a spool actually would be pretty easy on 
the write cycles, because you just create the file, never modify it, and 
eventually delete it. If your spool is small, you might be doing that a 
few times for a full backup, but even then it seems to me that there 
should only be a couple writes to each cell per day. Let's say that you 
spool and despool 10 times for a full backup.

I think even the cheapest flash memory has an MTBF of 10,000 write 
cycles, which means that an SSD used for spooling should last for 1000 
full backups - even more differential or incremental ones.

Or is my reasoning wrong here? Without practical experience, that's 
entirely possible.

-- 
Kevin Keane
Owner
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