From: Charley Bay (charleyb@cytomation.com)
Date: Sat Feb 28 1998 - 12:58:43 EST
The MO drive might actually have hardware compression on the drive itself, unlike a standard hard drive that might have software compression enabled through the operating system. So yes, it is possible that the MO drive is compressing your files automatically without you knowing about it. However, I think the more likely scenario is that the sector size in the MO drive is smaller than that used on your hard drive. If the file is 1 byte, but the sector size is 512 bytes, then the entire sector will be "reserved" for that file. The file can grow up to 511 bytes more and not actually take up another sector. Different utilities report file size differently... some may actually report the file as 1 byte, and others will call it 512 bytes (or some variation in between). Did the files shrink a lot (20-50%)? If so, I would guess you actually have compression. If they only shrank a little like you suggest (a few hundred bytes here and there), I would guess it's the difference in sector sizes. Since hard drives are getting so large, the industry trend is toward larger sectors. This leads to greater speed, but greater waste of space on the drive. The space is simply utilized more efficiently when you copy the same files to drives configured with smaller sectors. I hope this helps... --charley bay charleyb@cytomation.com ---------- From: David McFarland[SMTP:David.McFarland@mcmail.vanderbilt.edu] Sent: Thursday, February 26, 1998 10:39 AM To: cyto-inbox Subject: MO drives and CellQuest files I was doing my typical monthly backup of data and noticed something a little odd. All the CellQuest files that I copied to MO are slightly smaller than they were on the hard drive. However, they seem to contain all the data when reanalyzed. Is there some sort of low level compression going on with the MO drive? Anyone? David McFarland Howard Hughes Medical Institute Flow Cytometry Facility Vanderbilt University Medical Center
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